I tried the factory Para base pad extensions on my Mec Gar P/18 mags. As they come it's a no-go. The problem is the ridges in the sides of the mag bodies. On Mec Gar mags, they come down farther than on the Para mags. This prevents the insert from being pushed in far enough. I tried to mod an insert and it didn't work. But, I'm not giving up.