Starter Kit Contents (1) Gen 3 S15 magazines black nitride (1) GlockA(R) 43X / 48 steel mag catch black nitride Combo Kit Contents (3) Gen 3 S15 magazines black nitride (1) GlockA(R) 43X / 48 steel mag catch black nitride Mag Catch Requirement It is required to swap out your plastic OEM mag catch with either Shield Arms' standard steel mag catch or their premium steel mag catch. Here's why. If you don't swap your mag catch you may have reliability issues. If you use another manufacturer's mag catch you may have reliability issues. Gen 2 and 3 magazines were designed to work with Shield Arms steel mag catches. If you have a firs Mfg: Shield Arms