The 50 Ft. line set is insulated high quality copper tubing, which has been successfully tested by Method ASTM B743. The wall thickness of 1/4 "and 3/8" copper pipes are 0.65mm, the wall thickness of 1/2" copper pipes are 0.7mm. Seamless pure copper pipe shows no leaks With embossed polyethyene film, climate resistant foam, and 3/8 inch thickened insulated cotton, this three-layer insulated mini split copper line set is M1 level flame retardant, incorrodible, fireproofing, thermal insulation, shockproof, sound absorption and durable Our mini split line set won't crack at low temperature of -40 ℉, and has no deformation at high temperature of 248℉, ultra wide working temperature range, and can cooperate with all kinds of refrigerant operation Pre-flared ends with nuts are for simple and easy installation. Copper coil line set fits most ductless mini split air conditioners and heat pump systems Note: Because brands use different sizes, Please Check the AC brand's installation manual to get the right size, Manufacturer: ICOOL