Four interchangeable, high-intensity LitePipes are included with all M-Series sights allowing the shooter to adjust to existing light conditions. The S-Series includes a single LitePipe in your choice of green or red at a more economical price. HiViz?s snap on/off magnetic base is available in four different sizes to fit virtually any rib width from 11/64? to 9/16?. Refer to the selection chart for compatibility. Not compatible with fiber or aluminum ribs. S400 - Fits: Ribs from .328" - .437" (21/64 - 7/16", 8.3mm - 11.1mm). Fits Winchester: all post 1964 pumps and autoloaders; Mossberg: All (except ported models); Browning: Citori target grades (except super wide ribs); Beretta: S682 Comp, trap guns.