This is a Yankee Hill Machine Sidewinder piston cut for 14.5x1 left-hand threads, sized for .40 S&W hosts. On a tilting-barrel pistol, a suppressor's added mass can prevent the barrel from unlocking properly, so a booster piston, sometimes called a Nielsen device, lets the barrel move independently of the can and keeps the pistol cycling reliably.

Matching the piston to your host's thread pitch and caliber is what makes the difference between a suppressed pistol that runs and one that jams. YHM builds these to tight tolerances so the bore stays concentric and the pistol functions the way it should.

In stock and ready to ship straight to your door from Dawson Defense, an Arizona-owned licensed dealer.