G&G G16 Rotary Style Hop-Up Chamber for M4 Series Airsoft AEG Rifles

"Like the other guy said. Seriously, this is one of the best hop-up units on the market. Cheap, consistent and wont wear out other parts.

"fit with no issues w/ a madbull barrel and a 4UAD bucking into a DE UTR45. Was prob the easiest upgrade I've done... no mis feeding, no issues at all.

"I'm not even kidding, I buy these as upgrades. These are far better than Maxx hop up units.

"Even though this is made out of plastic don't be fooled into thinking the cnc version are much better. This by far has changed my aeg to become a long distance reacher of 100 yards. I'm a nerd - I own a range finder. I won't tell you what packing best pairs with this. Different factors come into play such as barrel length and the bore size. Not to mention the fps output. One thing I can say is if the packing you choose is tight fitting. That's a perfect match - you won't get fps drops on full auto