Larger version 1" valve uses a Rotor Disc ( 7185500, WS26X10010 ) and Seal Kit ( 7185487, WS35X10020 ) that is one inch wider in diameter. Rotor Disc is 4 3/8" in diameter. The standard version Rotor Disc ( 7199232 ) we sell is more commonly used and smaller ( only 3 3/8" in diameter ).