i bought this hop up unit about a year ago to replace my stock CA M16 hop up unit, mainly because it hah taken some damage and was on a budget. and i had read about plastic hop up chambers making guns a bit quieter.
from what i can tell, by using using this hop up unit over my stock CA unit, the fps from from about 420fps to 360fps. all of the same parts were being used (bucking, barrel, h-nub, ect.). i also could not tell any difference in the sound produced. additionally, the occuracy was slightly poorer than the stock CA unit.
after several months of using this unit, i switched back to my stock CA unit dispite its condition. i couldnt stand the drop in fps or the inconsistancy. the unit does work, but not very well.
-does its job
-easy to assemble and install
-speed dropped by 60fps
-bad color (i dont like to see a big red chunk of plastic when i open my dust cover)