Diamond Rock Extra Firm 12" Mattress

Diamond Rock Extra Firm 12" Mattress 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. Technology & Construction The Diamond Rock Extra Firm 12" Mattress is built in Diamond’s Southern California factory using their proprietary manufacturing processes. Diamond is one of the few mattress companies that makes their own pocketed coils, processes their own memory foams, and sews their own fabrics in-house. This vertical integration gives them direct control over every component and the ability to innovate faster than brands that rely on third-party suppliers. The mattress features CertiPUR-US certified foams, ensuring they meet strict standards for content, emissions, and durability. GREENGUARD Gold certification confirms low chemical emissions for a healthier indoor environment. Who This Mattress Is Best For The firm comfort level is designed for back sleepers and stomach sleepers who need a flat, supportive surface that prevents the hips from sinking below neutral alignment. Heavier sleepers (200+ lbs) often prefer firm mattresses because they maintain support under greater body weight without excessive compression. The firm surface also tends to sleep cooler because there is less foam material trapping heat around the body. Why Shop at LA Mattress Store As an authorized Diamond dealer, LA Mattress Store carries the complete Diamond lineup in all five of our Los Angeles showrooms — Glendale, West LA, Hancock Park, Koreatown, and Studio City. Walk in any time during business hours to try this mattress in person. Our sleep consultants can help you compare firmness levels, construction types, and find the right mattress for your sleep style and budget. Every purchase includes free White Glove delivery anywhere in the Los Angeles metro area — our team delivers to your room of choice, sets up the new mattress, and removes your old one at no extra cost. Same-day delivery is often available. Diamond offers a 120-night comfort exchange (exchange for a different model if needed) and a 20-year manufacturer warranty — one of the longest in the industry. LA Mattress Store coordinates all warranty claims on your behalf. We also offer 0% APR financing for qualified buyers, making it easy to invest in better sleep without paying the full amount upfront. Available Sizes Diamond Rock Extra Firm 12" Mattress is available in Queen, King, CA King, Twin, Twin XL, Full. Queen starts at $799. All sizes include free White Glove delivery in Los Angeles. Have questions? Call us at (800) 218-3578 or visit any of our 5 Los Angeles showrooms to try it in person.