The Firepower 0656-0015 FPTA Flame buster Torch Flashback Arrestors with Check Valves are recommended for all oxy-acetylene torches to control dangerous gas backflows. They provide ultimate protection against "flashback" in your oxy-acetylene system and are designed to prevent mixing of oxygen and fuel. The arrestors come with "B" 9/16"-18 threads, have high flow capacity and are 100% tested. Automatic shut-off design. Pack of 2.