These KCI USA's Glock pattern magazines are constructed with a hardened steel insert that is encased in a polymer. The polymer molding helps to protect the magazine body from damage and deformation from regular use.Features :Fits: Glock 17 / 17L / 19 / 19x / 26 / 34 / 45 / 47Caliber: 9x19mmCapacity: 17 RoundsBody Material: Hardened Steel / PolymerSpring Material: Stainless Steel