The Magpul GL Enhanced Magazine Well is designed to fully enhance and ensure positive magazine insertion in high stress scenarios. It is compatible with Gen4 Glock 17/22/31/34/35/37 and compatible with Magpul OEM and most aftermarket magazine floor plates as well as most common after-market magazine extensions. Recent generations of reduced capacity 10rd factory Glock magazines have several dimensional differences which may interfere with any magazine well. Including the Magpul GL Enhanced Magazine Well. Some large aftermarket floorplates may also interfere. *The Magpul GL Enhanced Magazine Well for Glock 17 Gen4 and Glock 19 Gen4 are not compatible as delivered out of the box with optional factory Glock Modular Back Straps. While end user modification is minor and may be attempted it is taken at own risk.