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.M400 - 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.