HATCO® DROP-IN SLIM FROST TOP FTB-S2.NSF 7 Approved Cold Wall Construction: This indicates that the refrigeration unit meets the standards set by NSF (National Sanitation Foundation) for commercial refrigeration equipment. Refrigerant that Keeps Food Cold Without Drying it Out: The refrigerant used in the system is designed to keep food products cold without causing them to dry out. This is important for maintaining the quality of stored food. Auto Defrost with Advanced Programmable