Glock switch

[7] The device is roughly the size of a United States quarter, and when installed on the rear of the slide on a Glock pistol (replacing the slide cover plate), adds a selective fire switch; flipping the switch sets the weapon to full automatic mode, which is capable of firing as many rounds per minute as the short-recoil action allows.

[9] A handgun with a Glock switch attached fits the definition of a machine gun under United States federal law.

[10] The 1986 Firearm Owners Protection Act made new machine guns illegal for civilians to own, banning "possession and transfer of new automatic firearms and parts that fire bullets without stopping once the trigger is depressed", with the exception of machine guns manufactured prior to May 19, 1986.

[11] The penalties for possession of an unregistered machine gun in the United States are up to a $250,000 fine and prison sentences of up to 10 years.

[10][12] In March 2022, a Vice News investigation learned that the federal prosecutions which involved conversion devices have been rising since 2017.