This 6/rd Glock magazine fits the G36 and comes in .45 ACP. 

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.