Serta iSeries® Hybrid 2000 12.5″ Firm Mattress $1,699.00 – $2,799.00 If it’s rejuvenating sleep you need, the Serta® iSeries Hybrid 2000 Firm might just be your perfect match. Featuring 3.5 inches of memory foam, this mattress offers firm support and supreme, state-of-the-art cooling technology. Boasting a 12.5-inch profile, wrapped coils and advanced memory foam, this mattress works to provide reliable, reinforced support and all-night comfort.