Discontinued by GSG.
This is the GSG magazine coupler for the GSG-16 22 round .22LR magazine.
Also fits magazines for the older GSG 522 and GSG 5 rifles.
Made from oxide coated steel with a spring loaded clamping mechanism it is an almost exact copy of the HK military MP5 magazine coupler design, scaled for the slightly slimmer GSG magazines.
Will not fit 9mm magazines.