It's a typical AT kit, with one minor modification. Instead of the mesh baffle, it incorporates a cardboard piston. Nice flyer on a G-80. I believe AT designed this for L1 certification as it really does nice on a middle H.
Although take my word for it, it will not fly far on an F21. (long story posted elsewhere with pix).
Nice beefy kit though.
I scrapped the piston and went to Kevlar as the piston simply would not fit -> no matter how much I sanded it.
A