NDZ Performance for Glock Gen 4-5 Grip Frame Slug Plug AL9 with Backstrap Installed Black Combat Medic 1 Engraved 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 1000+ High Quality Images Permanently Laser Engraved Images By NDZ Performance 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