Current mags only hold 10 rounds and have a button on the mag follower for easier loading, the originals hold 13. I have the 10 round ones and I had to do a bit of filing on the inside of the mags and on the sides of the followers as I found they would bind up a lot.

Got two of the new 20 round mags on the way The high capacity ones have a large delrin bump pad on the bottom of the mag.