AFM1: Fits over intake. Install the mount over aerator pump intake or 3/4" thru hull. Before installing nut and simply snap aerator filter in place. Black.AF1: Screws on over 3/4" or 1-1/8" pump intake fitting.BWF1: Fits over baitwell drains. Back injection molded base installs under flange on thru-hull fitting and the filter cap simply snaps on.