Oh boy, ugh let me put this way. When using the LEO adpater all you need to use is the AR buffer tube and jam nut, nothing else. With the recoil reducing system you are seeing with Mesa is the Endine system that looks like a buffer tube but isn't. Its basically a hydraulic piston that your MOE stock attaches to.
Buying a buffer and buffer spring and putting it in a stock tube will just make noise, not to mention good luck getting it in there.
*EDIT*
The pic mid page and the one furthest to the right is the shotgun unit.
http://www.enidine-defense.com/Recoilmain.html