Up for sale here is a single magazine coupler for Glock (and Glock
compatible magazines) for 9mm and .40 S&W calibers (NOT for 45 or
10mm calibers). I guarantee that these will fit factory Glock
magazines, aftermarket one should have the same dimensions (they all fit
the same magwell, right?), but due to low quality magazines in the
market I cannot guarantee fit (but they should by all means).