FD-2/2W: 4-1/4" overall dia. Mounts with 4 screws in a 2-1/2" dia. hole. FD-4/4W: 5-5/8" overall dia. Mounts with 4 screws in a 4" dia. hole. Both are designed with a flange molded into part to fit into hole so that cut or raw edges are hidden by floor drain.