You might not think of it this way usually, but fact is, firearm performance is about gas. That's where this official factory Remington® Gas System Kit comes in. The factory replacement parts that'll restore your shotgun to sharper functioning, the muzzle velocity and energy you should be getting. You get the nickel-plated piston / piston seal, and 3 Teflon® coated barrel seals (2 extras for down the road). Kit is exclusively for 12-ga. models.