Glock Magazines. These Glock Factory Magazine are designed to work. Double Stacked and Staggered for Maximum Capacity. We carry a diverse selection from high capacity to standard per model. Check your state laws and be sure you can own the magazines you are purchasing. A grip extension for Glock 29, also fits model 30 nine round magazines. A magazine grip extension replaces the magazine base plate increasing the total length of the magazine. Increasing the total length of the magazine provides for extra grip length which in turn stimulates superior control and comfort. They are made from High Impact Polymer.