Great hop up! i had a g&p after upgrading to a metal body and now that i have this it's like a whole different gun. I also purchased systema hop up bucking and tight bore barrel for my m4. Fixed all of my problems with jams and together increased my fps by alot.
the screw that holds the part that you rotate is to big thus letting the top gear wobble. It isnt a problem really though and the systems performance makes up for it.
Rating: [5 of 5 Stars!]