I can vouch for the fact they do NOT work on the 16 round mags. It won't go far enough in to lock up.
Same with a factory and Elander Witness 16 round mag.
It seems to be a very small amount one would have to remove from the top of the +2 base in order to make it work, but I haven't tried it yet.
Sent from my XT901 using Tapatalk