Reptillia Black Hole Polymer Magwell Glock Gen 3 and 4 Bases - Introducing the Reptilia Black Hole(TM) Polymer Magwell for GLOCK(R) pistols. Molded from reinforced polymer, the Black Hole's enlarged magazine well opening helps facilitate more efficient reloads without adding unnecessary bulk to your carry or duty sidearm. Compatible with 9mm & .40-caliber GLOCK pistols, the Black Hole utilizes a unique rear spacer to ensure seamless fit and compatibility with both Gen 3 & Gen 4 frames. Fits GLOCK 19/23 - Generation 3 Fits GLOCK 19/23 - Generation 4 Impact-Modified Reinforced Nylon Custom Alloy steel screw 8 grams