Got a plug for my old mossberg 500. Was told I needed to use with the shorter shells. After receiving plugs, I installed on shotgun tested cycling with and without the plug. Seems to work fine both ways??? Have not taken gun to rang an tested to see how it does when firing. Ordering an shipping was fast an easy, no problems at all. I well be hanging on to plugs even if not needed for my model. Never know may come in handy down the road.