Winchester Repeating Arms Magazine, 308 Winchester, 3 Rounds, XPR, Polymer, Black 112098802 The XPR's detachable box magazine is constructed of a light yet rugged polymer and securely latches at both the front and rear for added security and to endure feeding reliability. The magazine is a slick and slim single stack design that feeds cartridges in a straight line right into the chamber. Nothing could be more straight-forward. The XPR's magazine capacity is three cartridges in both magnum and standard calibers. Because they are so slim" additional loaded XPR magazines can be easily carried in your pocket or pack for a fast reload.