The pistol that started it all now enters its fifth generation, bringing with it all the features and accessories exclusive to the Glock Generation 5 pistol lineup while maintaining the familiar feel and renowned performance that its legendary reputation was built upon. The Glock Gen5 Magazine is compatible with previous Glock Gens. 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.