MCK | Best Glock Accessories | GlockStore.com Got this from the Glock Store and works great on my G17G4 and G19G5. I had to take my medium back straps off to get the weapons locked in the MCK-the locking tab will not engage. Taking the guns off was challenging as it was a tight fit. Its easier when I push the gun fwd then engage the release tabs and pulled back.