Low density polyurethane foam

There are three primary categories for polyurethane foam, with the lowest level labeled as low density polyurethane foam. Low density foam refers to the concentration of polyurethane within the material, and lower concentrations create a lower density. This type of foam is typically recommended for items that experience infrequent use, such as an outdoor cushion, an infrequently used custom mattress, and certain types of furniture cushion. Low density foams include R21 and R28 with a 1.3 pound density rating.