Standard factory Glock Magazines made of high resistance light weight polymer. This is a factory original, drop-free magazine for your factory Glock. Factory Glock magazines have a hardened steel insert encased in high tech polymer. This polymer coating protects the magazine and prevents deformation, even when dropped from a great height. NOTE: GLOCK MAGAZINES CAN BE VERY DIFFICULT TO LOAD WHEN NEW. OFTEN THE LAST ROUND WILL NOT FIT UNTIL THE MAGAZINE HAS UNDERGONE A BREAK-IN PERIOD. IT IS RECOMMENDED THAT THE MAGAZINE BE LOADED WITH ALL BUT THE LAST ROUND AND LEFT FOR A FEW DAYS TO COMPRESS THE SPRING. CYCLING THE MAGAZINE FROM FULL TO EMPTY MULTIPLE TIMES CAN ASSIST IN THE BREAK-IN PERIOD.