A protector keeps the warranty valid from night one — and it all rides along with your white-glove delivery, no extra trip.
The Rock is exactly what it sounds like: an extra-firm innerspring with a moisture-wicking quilted top and almost no soft layers between you and the coils. If 'firm' beds always feel too soft to you, this is the one. Most-recommended in our showroom for stomach sleepers and people with severe lower-back pain.
9/10 on our firmness scale. Almost no contour — your spine stays absolutely straight.
Quilted fabric pulls sweat away from skin overnight.
Reinforced edge support and high-gauge coils. Holds heavier sleepers without sagging.
Most extra-firm beds at this price are foundation-grade. This one's a real mattress.
A 9/10 firmness, supportive top with minimal contour. Best for back and stomach sleepers, plus heavier sleepers who want less hug.
Built for adaptive support and breathability. Every layer is hand-checked before it ships from our warehouse.
The Rock is Diamond's firmest build: a 12-inch extra firm mattress pairing Diamond's own in-house pocketed coil system with dense CertiPUR-US certified support foams and a reinforced tight-top surface, no plush quilting to soften the response. Diamond makes its coils, foams, and fabrics under one roof in Southern California, and the Rock uses that control to push firmness to the top of the range.
If every mattress you try feels too soft, the Rock is the answer: strict back and stomach sleepers, sleepers over 230 lbs who need maximum pushback, and anyone whose physical therapist recommended the firmest practical surface. An extra firm mattress like this also pairs well with a separate topper for sleepers who want tunable comfort over rock-solid support.
Diamond Rock Extra Firm 12" Mattress is available in Queen, King, CA King, Twin, Twin XL, Full. White Glove delivery is free in Los Angeles on orders over $499.
Diamond Mattress is a 4th-generation family-owned company that has been handcrafting mattresses in Southern California since 1946. Founded by the Pennington family in Compton, California (now headquartered in Rancho Dominguez), Diamond is one of the few mattress manufacturers in America that is fully vertically integrated. They make their own pocketed coils, process their own memory foams, and cut and sew their own fabrics, all under one roof. This level of control over every component means Diamond can maintain strict quality standards that outsourced manufacturers cannot match. Every Diamond mattress is CertiPUR-US certified, GREENGUARD Gold certified for low chemical emissions, OEKO-TEX tested for harmful substances, and ECO INSTITUT certified for environmental safety. Diamond also uses REPREVE recycled fibers in select products, demonstrating their commitment to sustainable manufacturing practices.
It has a extra firm feel, 9 out of 10 on our scale where 1 is the softest. It is a a weaker fit for side sleeping, great fit for back sleeping, and great fit for stomach sleeping.
From top to bottom it is built from Quilted moisture-wicking cover, Light comfort foam, High-gauge offset coil, and Reinforced edge in a 12-inch profile. Stays dry overnight
It suits: Stomach sleepers; Heavier sleepers (250+ lb); People with chronic lower-back pain; Anyone who hates the 'sink-in' feel; Larger bed frames that need rigid support. It is a weaker fit for: Side sleepers (will hurt shoulders / hips); Anyone under 130 lb; People with arthritis or pressure-point sensitivity; Couples with mismatched preferences.
Yes, free white-glove delivery anywhere in Los Angeles on orders over $499, including setup and free haul-away of your old mattress. Order by 4pm for same-day delivery.
You have our 120-night comfort exchange. Sleep on it for at least 30 nights, and if it isn't right, exchange it for another mattress, we handle the pickup and redelivery.
Yes, 0% APR financing through Synchrony on approved credit, plus Acima lease-to-own with no credit needed. Most applicants are approved in minutes at checkout or in any showroom.
Yes, our Los Angeles showrooms in Koreatown, West LA, La Brea, Studio City, and Glendale carry our lineup on the floor. Walk-ins welcome, no appointment needed.
