what's the deal with the green mag follower.

Joe, read Troy's magazine FAQ in the Magazine forum for a great education on mags.  The short version is that the green followers were to fix a jamming problem on rounds 28 - 30, which for some reason the military was never able to discover, occurred only on Sanchez magazines.  The green followers later became Mil-Spec.  The longer leg on the follower prevents it from tilting.

Troy, thanks for the correction.  I was not aware that the problem had occurred on the other manufacturer's magazines.

If you compare a green follower to a regular black follower, the difference is obvious. The green follower has 2 "legs", front and rear so it does not tumble over causing a feed jam. The black followers only have on leg, at the rear of the follower. This allowed for spring tension to cause it to advance up the magazine body rear up. This would become more of an acute angle as the magazine emptied, finally at about round 28 causing the follower to tumble butt end up. This caused the round to get lifted up instead of sliding into the chamber. The two legs on the greenie don't allow this to happen.

What about thermolds?? I have thermolds all with black followers, should this be fixed with green ones?

[beer]

I was told by a smith that the green ones were also harder/more scratch resistant and slicker than the black ones and actually slid up and down in the can better. Seems to work for me I replaced all mine with green ones.
Its $2.00 insurance!