|Ordered two of 'em, for the 4 PMAGs (gen 2) I also got. I found that I could not couple the two mags together...yet.
It seems the screw bolts are a tad bit too short? I cannot squeeze the coupler onto the mags tightly enough to thread the screw bolts. I'm going to try to get replacement screw bolts, about 4 to 5mm longer. Besides that, with only friction holding the two mags together, it is a nice setup.
Have to stagger the mags, left mag higher, to avoid the right mag interfering with the right, ejection side. And, have to have the coupler low enough on the mags to be able to fully insert into the mag well on a Sig M400.|