I get 21 in my P16 mags. Dawson pads, Arrendondo followers, factory springs. It is very tight though. You have to make sure they are seated completely and engage the mag catch. I usually load 20 in them so there is no problem with geting them to seat w/ a speedy reload. I could trim followers and maybe get one more in but I like the way it runs, yet to have a FTF. TXAG