Benefits Stops the pressure front and flame front. Stops gas from back feeding into the system. Prevents fire from being supported by gas. Signal lever will show if the pressure sensitive cut-off has been activated; the lever is also used for resetting the flashback arrestor. The Wilhelmsen Unitor W-66S Acetylene Flashback Arrestor is a safety device that prevents flashbacks from occurring during gas welding. Flashbacks can occur when a flame travels back through the hoses and into the regulator or cylinder, which can lead to an explosion or fire. The W-66S flashback arrestor works by interrupting the flow of gas if a flashback occurs, preventing the fire from spreading. The W-66S flashback arrestor is made of high-quality materials and is designed to withstand the harsh conditions of gas welding. It is also easy to install and use. The W-66S flashback arrestor is a valuable safety device for anyone who uses gas welding equipment. Note. For safety, we recommend annual testing and r