This NAICS Industry Group comprises establishments classified in the following NAICS Industries: 42371, Hardware Merchant Wholesalers; 42372, Plumbing and Heating Equipment and Supplies (Hydronics) Merchant Wholesalers; 42373, Warm Air Heating and Air-Conditioning Equipment and Supplies Merchant Wholesalers; and 42374, Refrigeration Equipment and Supplies Merchant Wholesalers.