Check the listing for details. Acetylene & Oxygen FLASHBACK ARRESTORS Reg End: Torch Welding, ISO 9001 cert. Condition: New. Listed at 17.95 USD. Oxygen-Acetylene (or propane) Flashback Arrestor Set. Attach at the regulator. Highest quality. 9/16 -18 threads, B Size. We also carry check valves for the torch end, which you can use in combination with these flashback arrestors. Please click here. NOTE: The acetylene arrestor in this set can also be used for Propane or Mapp gas, etc. Never connect a torch to acetylene and oxygen tanks without installing a set of flashback arrestors in the hoses at the regulators. Without these safety devices, it is possible a flash can occur within the hose, and ultimately follow back into the tanks, causing an explosion. This would be an extremely rare occurrence, but flashback arrestors will make it a "never" occurrence. Check valves are only a first line of defense and may not ultimately stop a flashback. Only the flashback arrestors will. ISO 9001 certified factory. If you don't see this certification, for your safety, it's best to not buy the arrestors. Thanks very much.