Ok if you are going to use Crspeed get the Versa pouch. It will come with all shims to fit a variety of mags. If you are looking at this style also have a look Jrholster pouches.
I put another post on here earlier, but I would strongly recommend considering the i-Shot mag pouches from MP-Store. I have the single and love it. My post is in the accessories section if you want to check it out. Good luck.
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