Tamers/Pistol grips use a short bolt that is included with the Tamer (no washer needed). 

Also fits: 
- Model 590A1
- Maverick model 88
- Other Mossberg pump shotguns that are copies or variations of the 500. 
- 510 Mini

Does not fit: 
- 930 series or any other auto shotgun. 
- Break open guns
- Flex system shotguns