Night Therapy’s Memory Foam 8 Inch Mattress and BiFold Box Spring set offers an excellent sleep solution for a healthy night’s sleep. Night Therapy Memory Foam is open cell memory foam offering improved airflow movement while providing a customized level of support. High density foam: Similar to memory foam mattresses, a high density foam mattress uses a more compact foam typically made from polyurethane.This kind of foam is made largely from open cells that are packed together tightly. High density foam mattresses offer comfort and longevity because they are more dense than a traditional foam mattress. .