Figured I'd mention that botach has them for $25. I have one on my m&p15 and it works great. Very similar to the Norgon ones, but a fraction of the cost. Just in case anybody was on the fence about getting one.
Battle Steel AR15/M4 Ambi-Mag Release - Botach

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Isaiah 43:1-3

Thanks, snm8510.

I don't have a need for an ambidextrous release, but I do like the way this particular one implements it.