Nine Ball "High Bullet Neo R" High Flow Valve for Airsoft Gas Powered Pistols
(Type: Umarex GLOCK)

"+20 fps
You have to align the valve properly or it won't work.
Watch the video.

"well I guess my last review got censored. dont waste your money! these DO NOT work in the mk23 unless you are using a low pressure gas.

"Bought for hi capa 5.1 works perfect very high flow worked great until I bought a new airsoft masterpiece frame that was very pricey some people say these don’t work usually when full of gas the problem is the hammer spring is not strong enough I had a aip 120% and worked until the new frame then would not fire I fixed the issue by removing hammer spring and putting one bb in hammer spring housing then the spring so it acts like a spacer to make spring stronger.

If you purchase this I recommend a 140% to 150% spring