Introducing the Reptilia Black Hole™ Polymer Magwell for GLOCK® 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. Note: Not compatible with 10 round factory Glock magazines but is compatible with Magpul® 10 round magazines.