Zev Technologies PRO Mag-well is designed for the professional shooter that is looking for the competitive edge of a mag-well without the bulk of a Glock race-gun. This mag-well is designed to fit both Gen 3 & 4 Glock frames which features a solid 1 piece designGen 4 back straps will need to be modified if usedCompatible Glocks G19, G23, G38, and G3210 Round magazines WILL NOT work with this model of mag-well. If 10 round capacity magazines are primarily used, this product is not recommended.ZEV Technologies PRO Mag-well 1st-4th Gen Glock® Aluminum one piece design in a matte black, smooth anodized finish. Includes mag-well, screw and wrench.--The mag-well is slightly flared at the base to be wider than the stock opening, which is ideal for quickly inserting the magazine in the pistol during reloads helping build proper muscle memory for improved consistency and reload time.--This ZEV Technologies PRO Mag-well is a great addition for any shooter looking for an edge with out the bulk flared competition style mag-well.--The addition of a mag-well will help keep the users hand in place while shooting.--Generation 4 back straps may need to be modified if used with this product, back straps must have bottom internal tabs trimmed. ZEV Technologies™ parts always incorporate design, feel and performance. Finally, all ZEV Mag-well components are designed to last, ZEV products are machined using quality aluminum materials.