MXT extension tube nut for Remington shotguns (see list below). This nut will replace your factory magazine cap and allow installation of an MXT shotgun extension tube. 

Fits: Remington 870 Remington 1100/11-87 
Remington Versamax 
ATI SX2 
Savage 720/745 
Some Tri-Star shotguns 
(may require modification)