Designed for repair use, for air condition, refrigeration and other equipments needing repair and fixing; for opening and closing compressor service valves, rotalock val ves and shutoff val ves Hvac service wrench set are metal, strong, and resistant. the bit adapter is heat-treated black coating 4 Different Sizes of Refrigeration Service Wrench Set: 1/4", 3/8", 3/16", 5/16", these sizes are the most commonly used sizes when repairing the air conditonning and refrigeration equipment Bit Adapter: 2 inch long, size: 3/16'' and 5/16 There are 3 types you can choose, 1 set curved ratchet wrench, 1 set straight ratchet wrench and 1 Hexagon Bit Adapter, Manufacturer: BOYANDM