"Definitely does what it's supposed to. Works for mp5 & g3 variant airsoft guns. This design is a little shorter than the one which is included with the t3-sas varients, but is long enough to mount red dot optics. I haven't tried any magnified scopes with it, but i don't forsee any problems doing that. I have heard that some people have issues with the shell ejection port not closing after they adjust their hop-ups... you're tightenng it down too far! It just needs to be firmly attached so it doesn't have any movement... don't crank it down super tight.
The only issue i have is that it's too short to mount a lens protector in front of my red/green dot, but i have a rather large optic, so no points off for that. I'm just giving it 4 stars because it's shorter than the one included with t3 mc51, & t3 sas varients."