Upgrade from 1 Pound Foam to 1 1/2 Pound Foam Spa covers come in varying densities of foam cores. Our stardard covers come with 1 lb foam and are also available in 1.5 lb and 2 lb. foam. The foam density is measured by pound per cubic foot. Increasing the foam density will increase the R-value and some weight to the cover. R-value describes a material's resistance to the flow of heat. The higher the R-value, the slower heat will travel or conduct through a material. Note: This item is available on the Classic and Prestige Models. It is not available for the Walk-On model. Upgrade to 1 1/2 Pound Foam Upgrade to 1 1/2 Pound Foam$43.50 Upgrade to 1 1/2 Pound Foam