Apex Tactical designs their striker blocks for performance, and installing this small part can make for a significant improvement. The geometry and dimensions of the striker safety plunger differs from the factory's so as to yield an exceptionally smooth uptake before the trigger bar engages the sear cam. That's why you'll find this component in nearly all their M&P and Shield kits. When installed properly, this drop-in kit will:Smooth trigger uptakeMinimize drag on the trigger barTactile, detectable trigger resetDirect drop-in replacement parts, no fitting required Notes:This kit is for use in any M&P series pistol, in any caliber, EXCEPT the M&P 45 Shield and not certified for use in the M2.0 Metal Series models.