Beautyrest Black L-Class

The Extra Firm build puts a thin quilted layer and a dense transition foam over the same T3 pocketed coil unit used across the line. At 8/10 there is almost no sink at the hips, which is precisely what stomach sleepers need to keep the lumbar spine from hyperextending.

What separates it from a cheap firm mattress is the coil unit's progressive response. The T3 wire still gives slightly under the shoulder even on the Extra Firm build, so side sleepers who occasionally roll over do not hit a wall. On our mat a 190 lb tester showed acceptable shoulder pressure on their side despite the 8/10 rating — unusual for a bed this firm.

Cooling: a 3.1°F surface-temperature rise after 60 minutes of loaded contact in our 68°F, 45% RH lab.

Edge support: 1.8 inches of compression under a 230 lb seated load at the perimeter.

Motion transfer: 0.13g peak with a 10 lb weight dropped 12" away.

Pressure relief: 35 mmHg peak shoulder pressure for a 165 lb side sleeper on an XSensor pad.

Response time: 0.5 seconds to fully rebound after release of a 25 lb compression.

Off-gassing: odor gone after 2 days in a sealed room with a trained sniff panel and a VOC sensor.

Durability: Pass on 30,000 cycles of our rolling load test (about eight years of nightly use).

Measured March 2026 under methodology v2.1.

Six-month impression measured 0.3 inches, the best result in the Beautyrest Black line, for the simple reason that there is less foam to compress. Firm beds with thin comfort stacks are consistently the most durable builds in the retail luxury segment.

Fit is the real question. At 8/10 this bed is wrong for strict side sleepers under about 200 lb, and it is wrong for anyone who describes their ideal mattress as 'cushioned.' If you are buying it because someone told you a firm mattress is better for your back, be aware that the evidence points to medium-firm for most people with lower-back pain — the C-Class is the safer choice unless you already know you prefer firm.