The Magpul GL Enhanced Magazine Well is designed to fully enhance and ensure positive magazine insertion in high stress scenarios. It fits Gen 4 versions of the: G17, G22, G31, G34, G35, G37, and is compatible with Magpul, OEM and most aftermarket magazine floor plates, as well as most common after-market magazine extensions. Recent generations of reduced capacity (10 rd) 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 Gen 4 and Glock 19 Gen 4 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.