The recent G21 mag I picked up with the +2 wouldn't lock the slide back. I pulled it apart to have a look at the spring and follower, all looked ok but I did tweak the top part of the spring where it connects to the follower as a temp fix and now it'll lock the slide back ok but I'd still like a new spring for this mag. So, I go to the Wolff web site and I'm looking around, figure it'd be the same spring as the G20 mag, NOPE, wrong, believe it or not the G21 mags take the same spring as the 19, 23, 26,27,29,30, 32 and 33. Basically the Compact and Sub-Compact guns. Who'd have thunk it, LOL. Of course it'd only be a +5% power spring in the 21 mag instead of the normal +10% power but still, I'd never figured that it was the same spring as the smaller guns. I guess if I could hunt down a standard base plate and just make it back into a 13 round mag I'd be fine but with the +2 I'm going to need a more powerful spring. Also, on a side note, the G30, 10 round mags that came with the gun seem to have thicker springs in em' then the G21 mag does and the color is different too. The G21 mag spring is kind of a bronze color and the G30 springs are a aluminum, white, metal, ect. color. I wonder if the G30 mag springs have been replaced at some point in time?