[R.I.T.Z]

I have never heard of CYMA putting out a GBBR.....
that being said according to the website

Replica of WA M4 Gas Blowback Mechanism

though "replica" has me worried.
I wouldn't cheap out on GBBR's get yourself a real WA or WE as most aftermarket parts are made for THEM and not clones, less fidgety ill fitting parts that may require modification to work....

Also considering CYMA isnt all that well known in the GBBR market I'd take that as a clue to tread very carefully