- A flat washer MUST be used with the factory stock bolt. A washer is included with the stock. The Hogue stock is designed to reuse the factory stock bolt with the addition of the flat washer.- The stock bolt (not included) is a 5 A 1/2"long 5/16" - 18 TPI with a flat washer available at any quality hardware store gun parts retailer or from Mossberg directly. You must use this bolt when changing from a pistol grip or Tamer to a butt stock. Tamers/Pistol grips use a short bolt that is included with the Tamer (no washer needed).- Forend adapter nut may be required for some models. #05020Also fits:- Model 590A1- 835 series 3 A 1/2" magnum pump shotguns providing adapter nut #05020 is used- Maverick model 88. Forend may require replacement of action bars (slide tube) with 7 A 3/4" "metal tube" type- Other Mossberg pump shotguns that are copies or variations of the 500.Does not fit:- 16ga 20ga or .410 bore shotguns- 510 Mini- 930 series or any other auto shotgun.- Break open guns- Flex system shotguns