The Glock 20, introduced in 1991, was developed for the then-growing law enforcement and security forces market for the 10mm Auto. The pistol will handle both full-power as well as reduced "FBI" loads that have reduced muzzle velocity. Due to the longer cartridge and higher pressures, the pistol is slightly larger than the Glock 17, having an approximately 2.5 mm (0.1 in) greater width and 7 mm (0.3 in) greater length. Though many small parts interchange with the Glock 17, with a close to 50% parts commonality, the major assemblies are scaled-up and do not interchange. The standard magazine capacity of the Glock 20 is 15 rounds. In 2009, Glock announced they would offer a 152 mm (6.0 in) barrel as a drop-in option.
The Glock 20SF is a version of the Glock 20 that utilizes the Short Frame (SF) which is based on the standard G20 frame (same width), but reduces the trigger reach from the back of the grip by 2.5 mm (0.098 in) and the heel of the pistol is shortened by 4 mm (0.16 in) so the trigger can be reached and operated better by users with relatively small hands.