Xd magazine base plate/extension - Pro Mag Springfield XD-9 Plus 4 / XD-40 Plus 3 Magazine Extension

I was skeptical at first due to the mixed reviews but by far impressed. Some will say it only adds one round but i found that if you change the follower to a spring internal in stead of the factory follower that has a piece of plastic down through the spring it frees up for room in the mag when the follower bottoms out. I have 16 total rounds in a factory 10 rd springfield magazine with a aftermarket follower with this base plate. Thats a whole total of 6 rounds with this base plate and aftermarket follower. FFT.