Uniweld Heat treated steel alloy and is plated to prevent rust. Trade specific tool for HVAC/R Technicians for opening and closing 3/16" and 5/16" hex liquid and suction base valves. Adapter has 3/16" and 5/16" hex keys included. For use with Uniweld's part# 70022 Reversible Ratchet Wrench and part# 70074 Offset Ratchet Wrench sold separately.