Slide Fire M&P Threaded Trigger Pins improve the overall mechanical reliability of the S&W M&P 15-22. These pins are anti-walking, and lock the pins into the receiver. Keeping them threaded in there will help prevent uneven wear that can lead to breakage. The pins are the standard size .156 inches. This kit includes 2 pins, 4 screws, and 2 Allen wrenches.