Glock 21 45 ACP 13 round magazine MF21013 is the large bore Glock magazine. This combat-ready mag has the same steel and polymer construction as the other Glock mags. These 13 round capacity magazines are factory made for Gen 3, 4, & 5 Glock 21 (MF21013) pistols. The G21 mags have a flush fitting Glock baseplate and numbered witness holes for identifying capacity.
Factory Glock Replacement Magazine