Energy Saving Design SpaMate covers are designed to seal in heat & moisture to save you money on energy costs. • Steam-Guard high R-Value core holds the heat in. • Hinge seal gasket holds in heat and prevents moisture loss. • 8 mil high density vapor barrier minimizes evaporation and heat loss. Need a extra heavy-duty cover with the highest R-value available? SpaMate 624® is available for all SpaMate covers. Designed to withstand heavy snowfall or the kids, SpaMate 624 has an industry-leading R-Value of 20 - so you'll save big on energy costs! To order, click on the 624 option on the order page.