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NM Cozy 12" Medium Firm Memory Foam Mattress - King
Free delivery as soon as Tomorrow, Jul 26 UnavailableComfort IQ™ Balanced medium feel — about 5–6 on the 10-point firmness scale, with memory-foam contouring. Versatile for back, side, and combination sleepers. Read Full Comfort Analysis
Meet NM® Cozy Memory Foam—all‑foam mattresses that pair cooling, temperature‑regulating comfort with low motion transfer, pressure‑point relief, and reinforced edge support. Thoughtful touches include hypoallergenic care, eco‑friendly manufacturing, adjustable‑base compatibility, and mattress‑in‑a‑box convenience.
An open bag mattress is a product whose original packaging has been opened, removed, or damaged. This includes showroom floor models, factory demo models, mattresses with damaged packaging, small scuffs/tears etc. The mattress itself is in excellent condition and comes with a full manufacturer's warranty. Read More about open-bag mattresses
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Our own take on memory foam
The NM 12″ Medium Firm Memory Foam Mattress is a medium (4/10) all-foam bed that pairs a deep gel-memory-foam comfort system with a high-density bio-foam support core, standing 12 in (30.5 cm) tall. Its balanced, slightly-softer-than-firm feel suits back and side sleepers who want cushioning with steady support, plus couples and light sleepers. Made in Canada, with a 365-night sleep trial.
Five layers, top to bottom. The specs name them and the Comfort IQ™ scores rate how they perform; here's what each one actually does.
| Size | Dimensions | Height | Weight |
|---|---|---|---|
| Single/Twin | 38″ × 75″ (96.5 × 190.5 cm) | 12″ | 30.8 kg · 68 lb |
| Twin XL | 38″ × 80″ (96.5 × 203.2 cm) | 12″ | 32.9 kg · 73 lb |
| Double/Full | 54″ × 75″ (137.2 × 190.5 cm) | 12″ | 43.8 kg · 97 lb |
| Queen | 60″ × 80″ (152.4 × 203.2 cm) | 12″ | 51.9 kg · 114 lb |
| King | 76″ × 80″ (193.0 × 203.2 cm) | 12″ | 65.8 kg · 145 lb |
Real per-size values from our catalog — weight differs by size; height is 12″ across the range. Price is shown live in the buy box.
The National Mattress promise
Made in Canada and sold by salaried experts — never commission. Free delivery, a 365-night trial, and a 10-year warranty on every NM 12″ Memory Foam Mattress.
In NM in-house testing it scores 8.5/10 overall, leading on pressure relief (9.0/10). For the full measured cooling, motion and pressure-relief scores, see the Comfort IQ™ performance breakdown below.
| Mattress Type | Memory Foam, Foam Core/No Coils |
|---|---|
| Product Features | Compatible with Adjustable Bed, Removable Cover, Cooling Technology, Temperature Regulating, Low Motion Transfer, Pressure Point Relief, Edge Support, Hypoallergenic, Eco-Friendly Manufacturing, Mattress In A Box |
| Trending & Offers | Best In Class, Top Rated, Most Popular, Limited Stock |
| Firmness | Medium |
| Core Type | NM® HD+™ High Density Support Core |
| Core Density | 1.8 lb/ft³ |
| Core Material | Polyurethane (polyfoam) |
| Brands | NM |
| Price Range | Great Value |
| Model | Chelsea CoolMax Pro Advanced 12" - King |
| Collection | NM® Cozy |
| Condition | Brand new, manufacturer sealed. |
| Warranty | 10 Year Warranty |
| Sleep Position | Side Sleepers, Back Sleepers |
| Cover Material | SoftLux Breathable Cotton |
| Colour | White, Grey |
| Quilt | Smooth stretch-knit surface (no quilting). |
| Comfort Layers | 2.5″ Gel Infused Visco Memory Foam, 2″ High Compression Bio-Foam |
| Support Layers | 1.8lbs Pressure Relieving Comfort Foam, 2.5″ Supersoft High Density Foam |
| Mattress Core | 5″ Optimal High Resilient Bio-Foam |
| Mattress Height in Inches | 12.00 Inches |
| Additional Features | Available boxed and rolled for easy shipping and handling. |
| Certifications | CertiPUR-US® certified foams. |
| Compatible With Adjustable Beds | Yes |
| Vented | Yes |
| Removable Cover | Yes |
| Handles | No |
| Assembly Required | No |
| Care Instruction | Removable cover unzips for cleaning — dry clean only to avoid shrinkage. Rotate head-to-foot every 3 months and always use a mattress protector to keep the warranty valid. |
| Country Of Origin | Canada |
| Manufacturer Contact Information | https://www.nationalmattress.ca/ |
| Shipping | Scheduled delivery with National Mattress. Please select your preferred delivery date in the checkout. |
| Single/Twin Size Dimensions | 39″ x 75″ (inches) – 99cm x 190.5cm (centimeters) - 65.8 kg |
| Single/Twin XL Size Dimensions | 38″ x 80″ (inches) – 96.5cm x 203cm (centimeters) - 51.9 kg |
| Double/Full Size Dimensions | 54.0" x 75.0" (inches) - 137.2cm x 190.5cm (centimeters) - 43.8 kg |
| Queen Size Dimensions | 60″ x 80″ (inches) – 152.5cm x 203cm (centimeters) - 32.9 kg |
| King Size Dimensions | 76″ x 80″ (inches) – 193cm x 203cm (centimeters) - 30.8 kg |
| Custom Sizes Available | Yes |
| Single/Twin Size Weight | 30.82 kg |
| Single/Twin XL Size Weight | 32.88 kg |
| Double/Full Size Weight | 43.8 kg |
| Queen Size Weight | 51.91 kg |
| King Size Weight | 65.76 kg |
| Product Supplier Code | NM-MF-SM-12-MD-KING |
| Product Category | Mattress |
| Product Type | Mattress - Foam Core |
| Product Sub Type | Memory Foam |
Comfort IQ™ · Scored on what actually matters
Comfort IQ™ scores eight dimensions 0–10 from National Mattress's in-house testing + construction — the same scale on every model, so two beds compare on what actually matters. Results vary by body type, base, and room temperature.
The NM 12″ Medium Firm Memory Foam is a deep, immersive cradle — Pressure Relief 9.0. Two and a half inches of high-density memory foam let the body sink in 2.51-3.52 inches, flowing around shoulders and hips so the heavy points stop bearing down, and the silent, near-zero-motion all-foam build makes it a genuine light-sleeper's bed. It pairs that deep plush cradle with a comfortable surface temperature (Cooling 8.8) for an enveloping, undisturbed night. For side sleepers, couples, and anyone who wants to melt in and sleep still, this immersive memory-foam bed is a perfect match.
An 8.5 overall built on a deep pressure cradle and near-best-in-line motion isolation, with the soft, sinking feel and all-foam edge as the honest trade-offs.
In National Mattress's in-house Comfort IQ analysis, the NM 12″ Medium Firm Memory Foam scores: Overall 8.5/10, Cooling 8.8/10, Pressure Relief 9.0/10, Motion Isolation 8.5/10, Edge Support 8.1/10, Responsiveness 8.9/10, Spinal Support 7.7/10, Durability 8.2/10.
A soft, plush medium with a deep memory-foam character — the two and a half inches of memory up top let you settle in and the surface rebuilds gently around the body. The thick 12-inch build gives a generous, immersive sink rather than an on-top feel. Sinkers will love it; anyone who wants to rest on the surface will find it a lot of give.
Cooling on the NM 12″ Medium Firm Memory Foam is where it trades comfort for honesty — the surface peaks in the 30.2-33.0°C range with the climb over baseline in the 8.2-11.0°C range, essentially level with an average bed, so call it neutral rather than cool. A SoftLux breathable cotton cover and a breathable poly layer move heat at the surface, but a deep, plush build you sink into hugs the body closely, and an all-foam core cannot vent warmth like an open coil chamber. By morning it eases into the 25.1-29.3°C range; an average sleeper stays comfortable.
Pressure relief is the headline on the NM 12″ Medium Firm Memory Foam — at a medium feel the body sinks in 2.51-3.52 inches, a deep, immersive, body-hugging cradle. The memory comfort layer flows around the shoulders and hips and spreads the load so the heavy points stop bearing down. Side sleepers, and anyone who collects tension in their pressure points, feel the give the moment they lie down — an almost weightless, enveloping contact. The flip side is real: if the sinking-in sensation is not your thing, this much immersion reads as too much.
For couples this is close to the best in the lineup — peak transfer reads in the 1.38-4.67 m/s² range, among the lowest anywhere we have measured, with movement settling out in the 0.54-0.76 second range. The deep memory-foam comfort layer swallows motion on contact, so a partner rolling over, climbing out, or getting back into bed barely registers across the surface. Paired with the dead silence of an all-foam build, it becomes a real answer if a restless sleeper next to you is what wakes you.
An all-foam perimeter is the honest weak point of a soft, sinking bed like this — with no coil ring or encasement bracing the sides, edge sinkage measures in the 3.74-5.80 inch range, so sit on the rim or sleep right at the edge and the foam gives noticeably under you. That is the expected behavior of a 12-inch plush foam build, not a defect. Out in the main sleep field it makes no difference; if you routinely use the side or want every inch edge-to-edge with a partner, a coil-encased bed holds firmer.
The NM 12″ Medium Firm Memory Foam answers pressure with a slow, controlled melt rather than a spring-back, which is exactly the point of a soft memory-foam build — total bounce travel comes in around the 5.07-9.81 inch range, and recovery takes a deliberate beat, the surface fully reforming in under 3.21 seconds and mostly settling in under 1.55 seconds. The memory foam yields gently and rebuilds around you. It feels cushioned and enveloping; the trade is that it is not a quick, athletic surface to switch positions on.
Break-in smell is a non-issue here — the off-gassing clears in 12-24 hours, with the initial odor rated Low. The foams are CertiPUR-US certified, independently tested against strict low-VOC limits, finished in Ontario and roll-packed right before delivery rather than spending months compressed in a box in transit, where an imported bed-in-a-box concentrates its scent. Unbox it, give it a day to breathe, and the faint new-foam smell is gone.
The medium, sinking feel is squarely a side sleeper's bed — the deep cradle lets shoulders and hips settle into the support rather than perch on top. Lighter and average bodies get the full immersive contour; heavier sleepers are still held by the dense HD+ core, though the deep sink may feel like a lot. Back and stomach sleepers who want a firmer lift under the spine, and dedicated hot sleepers, are the groups who may prefer a firmer or cooler model.
Full construction, per-size dimensions and coil counts are in the product description above. View 365-night trial details.
| Overall Score | 8.51 |
|---|---|
| Pressure Relief Score | 8.99 |
| Pressure Relief Ranking | Excellent |
| Pressure Relief Notes | All-foam build + thick gel-infused memory foam create a deep, body-hugging cradle at the shoulders and hips; Support foams stabilize the sink to prevent bottoming out. Great for side sleepers. |
| Spinal Support And Alignment Score | 7.7 |
| Spinal Support And Alignment Ranking | Very Good |
| Spinal Support And Alignment Notes | Alignment is a structural question, so judge it on what's underneath. Below the plush comfort layers sits a thick, dense NM HD+ high-density support core - firm foam that pushes back evenly across the whole surface and keeps the hips from dropping out of line with the shoulders. With no coils in the build there's no point-lift; the core does the alignment work uniformly. Because the medium top lets you settle into that support rather than perch on top of it, side sleepers are particularly well served here. Back and stomach sleepers who want a firmer lift under the spine will likely prefer a firmer model. |
| Support And Alignment Test Sinkage Depth | 2.51-3.52 inches |
| Support And Alignment Test Sinkage Feel | Extremely Deep |
| Support And Alignment Test Body Contour | Ultra Plush / Immersive Hug (maximum sink, highly enveloped) |
| Cooling And Breathability Score | 8.77 |
| Cooling And Breathability Ranking | Excellent |
| Cooling And Breathability Notes | Breathable cotton quilted surface; Gel-infused foams. |
| Cooling And Breathability Test Baseline Temp | 22°C |
| Cooling And Breathability Test Max Temp | 30.2-33.0 °C |
| Cooling And Breathability Test Ending Temp | 25.1-29.3 °C |
| Motion Isolation Motion Transfer Score | 8.49 |
| Motion Isolation Motion Transfer Ranking | Very Good |
| Motion Transfer Notes | Outstanding motion isolation: Slow-response memory foam helps absorb movement before it spreads; A thicker foam stack adds extra damping for partner movement. |
| Motion Transfer Test Accel Range | 1.38-4.67 m/s² |
| Motion Transfer Test Motion Duration | 0.54-0.76 seconds |
| Edge Support Score | 8.09 |
| Edge Support Ranking | Very Good |
| Edge Support Notes | A supportive bio€€˜foam core (1.8 lb/ft³) helps keep support more consistent toward the edges for sleeping closer to the side. |
| Edge Support Test Max Sinkage | 3.74-5.80 inches |
| Edge Support Test Lying Support | Fair |
| Edge Support Test Reinforced Edge | NO |
| Responsiveness And Ease of Movement Score | 8.93 |
| Responsiveness And Ease of Movement Ranking | Excellent |
| Responsiveness And Ease of Movement Notes | More contouring & slower to respond, so switching positions can take a bit more effort. Key factors: a thin memory-foam layer adds contouring without removing all the bounce; deeper sinkage adds a 'hug' that can make rolling over harder. |
| Response Test Mostly Recovered | under 1.55 sec. |
| Response Test Complete Recovery | under 3.21 sec. |
| Odor And Off Gassing Score | 8.5 |
| Odor And Off Gassing Ranking | Excellent |
| Odor And Off Gassing Notes | Break-in smell is a non-issue here. The off-gassing clears in under 12 hours, with the initial odor rated Low. The build is the reason: CertiPUR-US certified foams, independently tested against strict low-VOC limits, finished in Ontario and roll-packed right before delivery - not months compressed in a box in transit, where an imported bed-in-a-box concentrates its chemical smell. Unbox it, give it a day to breathe, and the faint new-foam scent is gone. The natural cotton cover keeps the whole build smelling clean. |
| Off Gassing Test Initial Smell Strength | Low |
| Off Gassing Test Off Gassing Period | 12-24 hours |
| Durability And Build Quality Score | 8.16 |
| Durability And Build Quality Ranking | Very Good |
| Durability And Build Quality Notes | How long this bed shrugs off body impressions comes down to the foam on top, over a core that doesn't fatigue. It runs a high-density memory comfort foam above an HD+ high-density support core - both built to hold shape far longer than the cheap low-density foam that softens and dents inside a year or two. There are no coils to lose tension and no edge ring to fail. Built in Ontario and backed by National Mattress's own 10-year warranty, its high-density construction is what makes that warranty a realistic promise rather than wishful thinking. |
| Brand Score | 7 |
| Brand Ranking | Good |
| Brand Notes | NM is National Mattress's own house line, made locally rather than shipped in under a national badge. The pitch is direct - the same construction spec as the brand-name beds sitting on the floor beside it, minus the licensing markup those names tack onto the tag. Because it's our own product, we stand behind it ourselves: the warranty is honored in-store by the people who sold you the bed, not handed off to a distant manufacturer's claims desk. What you're paying for is the foam and the build inside, not a famous label. |
| Bounce Test Max Depth | 6.35-8.53 inches |
| Bounce Test Max Rebound | under 2.91 inches |
| Bounce Test Total Bounce | 5.07-9.81 inches |
| Noise Notes | This mattress is silent, full stop. An all-foam build has no springs, no coils and no metal hardware - nothing that can squeak or creak when you roll over or a partner drops into bed. Spring mattresses tend to develop a telltale sound as their coils age; foam simply has nothing to make noise with, so it stays quiet for its entire life. Pair that silence with the excellent motion isolation and this becomes a particularly good fit for light sleepers, shared beds, and anyone the smallest night sound wakes. |
| Fiberglass Free | YES |
| Sleep Trial Score | 10 |
| Sleep Trial Ranking | Exceptional |
| Sleep Trial Notes | This NM bed comes with a 365-night sleep trial, one of the longest you'll find anywhere. Bodies need weeks to truly adjust to a new surface - especially a soft, sinking one if you're coming off something firmer - and a full year lets you live with it across every season. Sleep on it through summer heat and winter chill, and if it still isn't right when the window closes, you return it for a refund or exchange. It's a genuine year of nightly sleep to make the call, not a rushed few minutes on a showroom floor. |
| Value Notes | This is a sound, well-built buy where the materials genuinely justify the spend. You get a generous 12-inch profile with high-density memory foam over an HD+ high-density support core, a CertiPUR-US certified build, a natural cotton cover, local Ontario manufacturing, a 10-year warranty and a 365-night trial. It carries more comfort foam and height than the entry models, which is reflected in where it sits - but you're paying for real material and a deep, plush feel, not a marketing name. An honest value for a soft foam sleeper. |
At NM, we believe everyone deserves a great night's sleep without overspending. That's why our NM Brand mattresses are proudly manufactured locally, ensuring exceptional quality and unbeatable prices you simply won't find anywhere else.
Each NM mattress is thoughtfully crafted with premium materials and meticulous attention to detail, delivering outstanding comfort and support for every sleeper. By partnering directly with trusted local manufacturers, we eliminate unnecessary markups and bring you unmatched value.
Whether you prefer a firm mattress for optimal support, a plush surface for luxurious comfort, or something perfectly balanced, NM has the right mattress for your needs. Our wide range ensures you'll find the perfect match without stretching your budget.
Locally Manufactured: Supporting Canadian craftsmanship and quality control.
Superior Value: High-quality mattresses at unbeatable prices.
Variety and Versatility: Comfort options to suit every sleep preference and budget.
Durable and Reliable: Built to provide lasting comfort night after night.
Discover the NM difference—affordable, comfortable sleep that's locally crafted for your best night's rest.
We offer FREE DELIVERY to all major cities in Ontario on orders over $199. A delivery surcharge of $45 applies to orders under $199.
Select your delivery date at checkout and add any special instructions in the order comments. You'll receive a 2‑hour window and live tracking on delivery day.
We ship select roll‑packed mattresses to all provinces (YT, NT, NU excluded). View Canada-wide shipping options →
View complete delivery information including FAQs, or contact our team directly.
It sits at the soft end of medium, a 4 out of 10, so it leans softer than a classic medium-firm. You sink into the gel memory foam in the 2.5 to 3.5 inch range, which gives a deep, cradling feel rather than a firm push-back. Side sleepers and lighter...
No box spring is needed. As a 12-inch all-foam mattress it wants a solid, flat, fully supportive surface: a platform bed, a slatted frame with gaps no wider than about 3 inches, or a bunkie board over an older box spring. A traditional sprung box spring...
Yes. The all-foam build flexes freely with an adjustable base, and with zero coils there is no spring system to fight the bend or wear at the hinge points. It is listed as adjustable-base compatible. The 12-inch height and slow-recovering memory foam...
Yes, this is one of the strongest in our lineup for couples. Motion isolation scores 8.5 out of 10, with measured peak transfer as low as 1.65 m/s2 and movement settling in well under a second. The deep memory foam absorbs a partner rolling over or getting...
It sleeps neutral, not notably cool. We measured a peak surface temperature around 32.6 C, essentially level with an average bed, earning a cooling rating of 8.8 mainly from a breathable cotton cover and poly layer that move heat at the surface. The ...
Edge support is the honest soft spot here. With an all-foam perimeter and no coil ring, the edge compresses noticeably when you sit on the side to dress, measuring sinkage in the roughly 3.7 to 5.8 inch range. That is normal for a plush 12-inch foam ...
It is built to resist sagging with high-density memory foam over an HD+ high-density support core, both rated to hold shape far longer than the cheap low-density foam that dents within a year or two. National Mattress backs it with a 10-year warranty...
Barely, and it clears fast. Because it is roll-packed in Ontario right before delivery rather than compressed in a shipping container for months, the initial odor is rated Low and dissipates in under 12 hours. The foams are CertiPUR-US certified and ...
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