I'm not entirely sure what generation the fusion engine is but it looks like a gen 2 or 3. Scar needs a new hop up unit. The fire selector had to be removed because the fire selector plate is for an m4. If you buy a vfc scar selector plate and put it on then it should work just fine. Fire selector is included. The acog is basically useless because it's way off to the left. Will include: - the SSR with a fusion engine - a bag of random scar parts (screws, springs, fire selector, mag release, stuff like that) - original box for the fusion engine with some spare parts in there (red and blue m4 nozzles will be included) - (not pictured) basically boneyard regulator, 2x fcu lipos, and a tank that I'm not sure of the hydro date (probably has about another year on it) Price is shipped and OBO No trades PayPal only