It fits perfectly on single size mattress. There is a clear silicon urethane panel over the top surface of Biomat showing the amethyst gems to shine through and also for an extra comfort. You will get a molecular level massage and increased blood circulation. The Biomat replicates the effects of a sauna except it allows a more customized temperature regulation without the hazards of heating the head or the negative EMF exposure in traditional saunas or heating devices. Richway mat has been designed so that the Amethyst crystals can produce the most beneficial frequency of vibrational energy that the human body can absorb, thereby promoting increased conduction and absorbtion of Far Infrared Rays and Negative Ions. (Amethyst pillow sold separately)