CNC MAX Aluminum Hopup Chamber for AK Series Airsoft AEG Rifle by Matrix / SHS

"I just installed this hopup in my JG AK74. The picture shows two different models; not sure why. The one I received was the blue one. I kept the parts/pieces from the original hopup as this unit came w/ none.
It was necessary to do some minor modifications to the unit and my gun to get everything to work. Almost anybody could do this.
Where the motor housing and the hopup come together, there is a tab with a screw through it. This tab goes in between the upright portion of this hopup. This was not how the original polymer hopup was installed as it did not have this feature on it. This tab is a little too wide to go between the upright portion. I removed the screw from the tab, lightly filed down both sides (this was easy as the housing is pot metal) and then slid the hopup around the tab and reinstalled the screw.
Next was the pin that is installed w/ the hopup lever. The hole for the pin in the Matrix unit is slightly tighter than the original. The original pin would not fit. I had to find the right drill bit size to open the hole up so the pin would insert but still remain tight enough.
Lastly, the profile of the pickup tube on the bottom of the unit for the BB's is slightly different to the point that none of my mags would lock in. Not even close to locking in. It appears the profile is constructed heavier/thicker on the Matrix so it doesn't push the button inside the mag at quite the right spot to make it all slide together. Easy fix. I used a Dremmel (could've used a fine toothed file too) to lightly reduce the profile a little bit on the back side of the hopup's BB pickup opening. This right where the hopup and the button inside the mag meet. By lightly filing this back side, all my (various) brands of mags work seemlessly. I used a very fine grit with the Dremmel and it came out very smooth. I didn't want any rough spots chewing on my mags.
So that's it. The Matrix hopup, a Prometheus barrel, and a new bucking later and my gun is back in the game and performing (accuracy and distance) way better than it was new, out of the box. No duh, right?
I hope this helps anyone thinking about this unit or having an issue w/ installation. And the the people at Evike have been top notch in helping me get the parts I needed and resolving some issues. Just talk to them. They'll get you steered in the right direction.

"As description says, is a clone (or oem?) of the prowin.

Not going into pros and cons, because with these things the only real pro is that it works like it's supposed to, which this does. So "quirks":

-It's an incomplete package. They expect you to be replacing a stock hopup so screws and brass spacer aren't included. Also the bottom fastener it comes with does not have a plastic protrusion at the bottom to fit in the groove of the inner barrel, this plus the looseness (see below) means it can rotate around. Just use the stock fastener instead and it's not an issue.

-It's kind of loose. Stock rubbers can fall right out. On the other hand, certain rubbers like madbulls will fit more easily, and you've got more breathing room to do the dental floss mod. I permatex all my hopups so again, this hasn't been an issue for me.

-My biggest beef with this thing. When it first came in the hole from the feed tube to the hopup chamber was way too narrow. Couldn't even push the BBs in with a cleaning rod, much less feed normally. I ended up having to sand it down with a dremel. Not something that should need to be done.

Honestly, between floss, teflon tape and permatex, stock hopup units are fine to keep (nubs and rubbers are a whole different matter). I got this purely because I needed one for a custom build and this and the prowin are the only aftermarket AK hopups I've found that screw to the gearbox a la, E&L, LCT, APS and others. Unless you're like me and paranoid about those two grub screws that E&L and LCT love to use to hold in their front assemblies, other options, even no option at all, may be better.