Glock 21 mags and Extensions

[USMarineVMA542]

I have a cmmg banshee in 45 acp and just picked up a Kriss vector in 45 acp. Looking to stock up some good mags, I don’t know that I want glock factory mags since I’d like to buy extensions for them.

Any recommendations on aftermarket g21 mags, good deals on g21 factor mags or thoughts on the mag extensions?

Thanks and SF!

 

[ACC]

These are GTG

https://www.etsgroup.us/ETS-Magazines-for-Glock-s/1823.htm?searching=Y&sort=5&cat=1823&show=30&page=1&f-.45%20cal=1871'