Cover snaps over mounting flange dimples to conceal screws. Concealed mounting flange is 3 1/8" OD diameter with two screw holes and three locking dimples and is 1/8" thick, type 304 stainless steel. Cover is type 304 stainless steel with satin finish, 22 gauge, 3 3/16" diameter. Snap Flange (1-1/4? O.D) Smooth.