The Rv Thermo Pigtail (Type I Acme) Provides A Safe, User-Friendly Connection From Your Marshall Excelsior Megr-253 Regulator To A Standard Lp Gas Cylinder Without The Use Of A Wrench The Easy To Tighten Nylon Nut Swivels On A Connector Fitting That Is Heat Sensitive Between 240 Degree And 300 Degree The Brass Nipple Displaces (Approximately 14), Closing The Cylinder Valve Module And Stopping The Flow Of Gas From The Container Inside The Brass Nipple Is A Flow-Limiting Device Designed To Sense Excess Gas Flow If Excessive Gas Flow Is Detected, The Rv Thermo Pigtail Will Shut Down The Flow To A Maximum Of 10 Scfh (By-Pass Flow) This Product Is Required By Rvia (Recreational Vehicle Industry Association) As Original Equipment On Your Rv And Should Be Maintained To The Highest Standards Because Of This Required Standard, When Opening Or Refilling Your Lp Gas Cylinders, It Could Take As Long As 20 Minutes To Re-Pressurize Your Lp Gas System For Normal Appliance(S) Operation