Blue, 2 lb. density, 1/4" thick closed cell foam. Because this Spa cover is manufactured from 'closed cell' foam it will not absorb water. Unlike other thermal spa blankets, it's not necessary to coat the foam to keep the water out. By eliminating evaporation a floating cover can reduce the operating costs of a spa in numerous ways. Blankets over 5’ wide consist of two pieces of foam “welded” together. These blankets can be cut to size with household scissors easily. Heat travels through moist air much quicker than dry air. Reducing the moisture between the water surface and the insulating spa cover will cut down greatly on heating costs.