Rugged, impact resistant exterior coatings. Holds up under severe conditions; Tamper proof mechanical-fit air valve. No heat distortion from brazing. Recessed to prevent damage during shipping;Deep drawn steel shell. For added structural strength. Maximum working pressure 125 psi. (Except: V45MP & V60MP);Steel inner shell and insert. Prevents over expansion of diaphragm for longer life;This new diaphragm design has improved diaphragm life by reducing abrasive wear. The diaphragm separates air and water to maintain the tank’s air charge. The Butyl rubber diaphragm is an FDA approved material and also meets NSF / ANSI 61 – G standards;Rigid polypropylene liner. Meets FDA and NSF requirements, providing maximum corrosion protection. Water never touches metal;Patented positive retention system. Securely fastens diaphragm and liner for years of reliable service;Stainless steel system connection. For optimal corrosion resistance;High density polyethylene is structurally reinforced for added strength. High profile design provides easy access for water hookup