Multi-layered foam construction creates good night sleep GranRest 9-Inch HD Memory Foam Mattress. Highly breathable gel infused memory foam improves heat transfer and dissipation within the mattress. The result is stunning: actively dissipates heat. This mattress includes 3-4 different layers which are I-Gel foam, high density (HD) convoluted foam, and high density (HD) foam. All these different materials work together to contour and conform to your body shape and movements, resulting in a restful and rejuvenating night.