The Glock 19 is effectively a reduced-size Glock 17, called the "Compact" by the manufacturer. It was first produced in 1988, primarily for military and law enforcement. The Glock 19's barrel and pistol grip are shorter by about 12 mm (0.5 in) than the Glock 17, and it uses a magazine with a standard capacity of 15 rounds. The pistol is compatible with factory magazines from the Glock 17 and Glock 18, giving the Glock 19 available capacities of: 17 rounds (standard magazine with +2 extension), 10, 17, and 19 (standard Glock 17 magazine with +2), 24 and 26 (standard magazine with +2 extension) and the 31 (standard Glock 18 magazine with +2 removed) and 33 rounds of the Glock 18. To preserve the operational reliability of the short recoil system, the mass of the slide remains the same as in the Glock 17 from which it is derived. With the exception of the slide, frame, barrel, locking block, recoil spring, guide rod, and slide lock spring, all of the other components are interchangeable between the models 17 and 19.