Perko's 0520DPGCHR Chrome Fuel Fill is for use with a 1-1/2" hose on gas applications only. A Deck Plate key and an O-Ring are included. There is a retainer on the cap and the cap has a slot between the holes. This Fuel Fill is constructed with chrome plated bronze material for long-lasting use. The outer dimension of the Flange is 3-1/8" and the neck length is 3-1/2". The mounting hole diameter is 2-1/8" and a #8 screw size is required for installation.