Firm vs. Extra Firm: Why Dual-Coil Mattresses Feel Different

The Green Mattress: Firm and the Extra Firm arrive at firmness in two different ways. The Firm uses one 8-inch coil unit that varies its wire diameter by body zone. The Extra Firm uses two 3-inch coil units stacked one above the other, separated by a pad of organic coconut fiber infused with organic latex. That structural difference is why the two mattresses feel distinct underneath you, and why the Extra Firm holds its surface under load in a way a foam-firmed mattress does not.

Most mattresses sold as "extra firm" get there by adding density to a foam layer. We get there by adding structure, a combination of engineering and material design.

Both are GOTS certified organic at the finished-product level. Both are hand needle-tufted with organic wool rosettes rather than glued. Both carry the same six finished-product certifications.

Firmness is not one property. It is the sum of two: what the surface does when you first lie down, and what the structure does after four hours of your full body weight concentrated at the hips.

Most mattresses solve the first and neglect the second. A high-density polyurethane or memory foam layer reads as firm on a showroom floor. Foam firmness is a material property, measured as indentation load deflection, and it changes as the cell structure fatigues under repeated compression. The mattress that felt firm in year one feels different in year six, and the change shows up first in the exact spot where you sleep.

Coil firmness is a structural property. A tempered steel spring returns to its original geometry after compression, and double-tempering, which means heat-treating the wire twice, raises the load at which the spring takes a permanent set. The firmness comes from the geometry of the system rather than from the density of a material that softens.

That is the engineering argument for building firmness out of steel and natural fiber instead of foam. It is also the reason there is no polyurethane foam in either mattress. GOTS certification at the finished-product level prohibits it, and the certification is what holds the design honest.

The Firm uses a single 8-inch unit of individually wrapped coils arranged across seven ergonomic zones, each coil encased in food-grade non-woven polypropylene so it compresses independently of its neighbors.
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Every coil in the unit is 14-gauge double-tempered recycled steel. Unlike the Medium, Plush, and Ultra Plush, which vary firmness using three different wire gauges, the Firm varies wire diameter by position within a single gauge:

The thicker wire runs through the center hip zone, where the heaviest concentration of body weight lands, and around the head and foot perimeter, where mattress structures compress and degrade first. Thinner wire at the shoulder allows the shoulder to settle rather than be propped up, which is what keeps the spine level rather than arched.

Above the coils sit two cocofiber pads and 2 inches of GOLS-certified organic Dunlop latex, then organic wool, then a quilted GOTS-certified organic cotton cover. Nothing is glued. The layers are secured by hand needle-tufting with wool rosettes, which is also what allows the mattress to meet federal flammability standards using wool as the flame barrier rather than a chemical treatment.

The result is a taut, responsive surface with meaningful give. A 7 out of 10.

The Extra Firm replaces the single 8-inch unit with two 3-inch units stacked one above the other.

Both units are uniform 14-gauge double-tempered recycled steel throughout. There are no softer comfort coils and no transition coils anywhere in the system. Between the two units sits a 0.5-inch pad of organic coconut fiber infused with organic latex.
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Paired with our Heavy Duty Foundation, the system is engineered to support up to 2,000 pounds. The whole mattress stands 9.75 inches tall, which is lower than most mattresses marketed to heavier sleepers.

Three mechanics account for the difference.

Shorter coils travel less. A 3-inch coil has less distance to compress than an 8-inch coil before it approaches its load limit. Two 3-inch units stacked reach roughly the same total height as one 8-inch unit plus its buffer, but the sleeper is supported by two short, stiff springs in series rather than one tall one. Short springs deflect less under the same load. That is the primary source of the Extra Firm's 10 out of 10 feel.

The coconut fiber pad spreads load laterally. Both mattresses use cocofiber. What differs is where it sits. In the Firm, two pads work within the comfort system above the coil unit. In the Extra Firm, a 0.5-inch pad infused with organic latex sits between the two coil units, and that position changes what it does.

Individually wrapped coils are precise. Each one responds only to the pressure directly above it, which is what produces contouring and motion isolation. Stack two pocketed units directly on top of each other and that precision compounds into a surface that feels loose under concentrated weight. The pad between them acts as a semi-rigid plane. It distributes a point load across a wider footprint of the lower unit, damps the motion passing between the two layers, and adds firmness of its own. Coconut coir infused with organic latex is dense, resilient, and open enough to move air.

Two independent arrays share the load. When the upper unit reaches meaningful compression, the lower unit is still near the top of its travel. The system has support in reserve at the loads where a single-unit mattress has already flattened. This is what "does not bottom out" means in practice, and it is the reason the Extra Firm is the model we recommend for heavier bodies.

There is a fourth effect that is not about feel. Two coil units plus a coir pad is a mostly open structure. Air moves through it. Solid foam does not permit that, which is why foam mattresses need gels, phase-change finishes, and surface treatments to manage heat. Ours moves air through the architecture, wicks moisture through organic wool, and breathes through perforated latex. The cooling is a property of the construction rather than a layer added on top of it.

"Dual-coil" describes two different architectures in our lineup, and they are not interchangeable.

Two stacked support units, as in the Extra Firm: equal-height, equal-gauge, built for load capacity and maximum firmness.

A micro-coil comfort layer over a base unit, as in the Luxury Organic Pillow-Top, the Luxury Organic Box-Top, and the Wool Mattress: a 1-inch layer of smaller, more numerous springs sitting above the 8-inch base. Because those coils are small and closely spaced, they respond to finer differences in body shape. That architecture adds contouring and motion isolation. It makes a mattress softer and more responsive, not firmer.

Same two words, opposite intent. If a coil count is being compared across models, this is why the comparison rarely means what it appears to mean.

Firmer foam is the cheaper answer, and it is the standard one.

Build an extra firm mattress out of high-density polyurethane and the bill of materials drops, the mattress compresses for shipping, and the showroom feel is convincing. The tradeoffs arrive later: the foam fatigues under repeated compression at the point of heaviest load, it traps heat because it is a closed structure, and it is a petroleum-derived input that no organic standard permits in a certified finished product.

We are constrained on that last point by our own certifications, and the constraint is the point. GOTS certifies the finished mattress, not a component inside it, and it prohibits polyurethane foam, memory foam, fiberglass, PVC, and chemical flame retardants in the certified product. Once those materials are off the table, firmness has to be engineered from steel, coconut fiber, latex, and wool. That is a harder design problem and a more expensive one. It also produces a mattress with a 25-year warranty.

The materials that make the Extra Firm safe to sleep on and the materials that make it hold its shape are the same materials. That is not a coincidence in the design. It is the design.

Choose the Firm if you sleep primarily on your back or move between positions, you want a taut and responsive surface with some give, and you want zoned support that lets the shoulder settle while holding the hips level.

Choose the Extra Firm if you sleep on your back or stomach, you are a heavier or big-and-tall sleeper, you are an athlete who wants minimal sinkage, or you have simply never found a mattress firm enough. Side sleepers who want this level of support underneath can add an Organic Mattress Topper for shoulder and hip contouring.

If you are between the two, the Firm is the safer choice. The Extra Firm is genuinely a 10.

Both carry a 1-year sleep trial and a 25-year warranty. The Extra Firm ships flat with in-home delivery and setup, and it requires a properly designed support system to maintain warranty coverage. We recommend the Heavy Duty Foundation.

The Firm is a 7 out of 10 and uses one 8-inch pocketed coil unit across seven zones, with wire diameter varied by body zone. It stands 11.5 inches tall. The Extra Firm is a 10 out of 10 and uses two 3-inch pocketed coil units stacked and separated by a 0.5-inch cocofiber pad infused with organic latex. It stands 9.75 inches tall. Both use 14-gauge double-tempered recycled steel, 2 inches of GOLS-certified organic Dunlop latex, and GOTS-certified organic wool and cotton.

A dual-coil mattress uses two separate layers of springs rather than one. In the Avocado Extra Firm, both layers are 3-inch support units of equal gauge, which increases firmness and load capacity. In the Luxury Organic Pillow-Top, Box-Top, and Wool Mattress, a 1-inch micro-coil layer sits above the 8-inch base unit, which increases contouring and motion isolation. The two designs produce opposite results.

It depends on the design. Two stacked support units of the same gauge are firmer, because shorter coils deflect less under load and two arrays share the weight. A micro-coil layer added above a base unit is softer, because the smaller springs contour more closely to the body.

Up to 2,112 in a King, counting both units. Queen is 1,600, Full is 1,426, Twin XL is 1,024, Twin is 992, and California King is 2,108.

Not on its own. Wire gauge, coil height, encasement, and zone architecture matter at least as much, and coil counts are not comparable across different architectures. A stacked dual-support system and a micro-coil comfort system will report similar totals while doing entirely different jobs.

Both mattresses use cocofiber, but in different positions. The Firm uses two pads within the comfort system above the coil unit. The Extra Firm uses a 0.5-inch pad infused with organic latex between its two coil units, where it distributes load across the lower unit, limits motion transfer between the layers, adds firmness, and keeps the structure open to airflow. In both cases, it lets the layers be assembled without glue or synthetic foam.

For many back and stomach sleepers, yes. The dual-coil system is designed to keep hips and shoulders level and limit sinkage at the lower back. Side sleepers who need pressure relief at the shoulder and hip will likely find it too firm on its own and should consider a topper or a medium-firm model. This is general product information, not medical advice.

It is built to breathe rather than to be treated. Two open coil units, a coir pad, perforated organic Dunlop latex, and organic wool that wicks moisture all move air and heat away from the surface. There are no cooling gels or chemical finishes in the design.