Rocksarge - great pics and they show a lot. Follower is different and it looks like the actual mag body shape/design is different at the top opening (in plan view looking top down) which seats the follower. The PPQ red follower has that "hook" to the left and it appears the mag body is shaped outward to accommodate it whereas the P99 does not and is shaped differently. And the depth and shape of the follower bottoms are different which may account for the 16th round. I'm kind of surprised it seems to work as well as apparently it does in a PPQ - wonder if it rattles in the PPQ given the external shape at the top/follower area. On the other hand, I'd expect an issue way before 150 rounds. I may try a couple as range mags. Again, thanks Rocksarge, great post! (BTW, what types of ammo have you tested them with so far: fmj, jhp's, 115gr, 124gr, 147gr etc? thx)