The Apex Tactical M&P Barrel Fitting Jig gives you a stable platform that makes final fitting of Apex Grade Gunsmith Fit M&P barrels easy and consistent. The M&P Barrel Fitting Jig has a cutout that securely cradles the barrel, with a channel to guide your file so you can properly square the barrel lugs. There’s even a setscrew to lock the barrel firmly in place during filing; screw has a nylon tip to protect the surface of your barrel from damage. Designed for use with Apex Grade Gunsmith Fit barrels for Smith & Wesson M&P Can be used with other aftermarket M&P & Glock barrels Sturdy machined aluminum construction Recommended: use a ½" safe edge Equaling or Parallel file with the jig. Many other files are tapered, which will cause uneven contact points Apex includes with the M&P Barrel Fitting Jig a jig slider that helps you maintain consistent pressure on the barrel while you fit the crucial bottom lug.