Carlson's Graphite coated Gas O-Ring Assortment Kit is for long lasting performance in your autoloader. It is compatible with 12 and 20 gauge Remington Model 1100, 11-87, Pro Bore Guns, G-3 models; Beretta shotguns; Winchester shotguns; Franchi shotguns; Tri Star shotguns; EAA shotguns, and many other shotguns that use a gas o-ring. *20 gauge rigs will fit most 28 gauge.