NDZ Performance for Glock Gen 4-5 Grip Frame Slug Plug AL9 with Backstrap Installed Black Plain NDZ AL9 Black Aluminum Grip Plug for GLOCK 17 18 19 22 23 24 25 31 32 34 35 37 - GEN 4-5 ONLY - use with BACKSTRAP INSTALLED Plain Black - No Logo Fits flush, prevents snagging, debris from entering or reaching trigger assembly and firing pin Quick install and easy removal, uses spring plunger assembly for retention 100% Aluminum - NOT plastic. Also helps guide mag. into magazine well