Solid product, but fitment is a mixed bag. - Vism AR Blastar Thumbhole

Firstly, the piece is solid and tight. Installed easily once I bothered reading the instructions. The length of pull is alright and the grip has a nice solid feel. Fitting against the boss is tight and firm, but (at least on my lower) doesn't fit flush around the outside curve. It's only a fraction of an inch, but it's noticeable. This is a well made (here's that word again) solid part that doesn't give a cheap vibe like you'd expect of something at this price point.

I have 2 of them at this point, so I'm obviously satisfied. Note: this fits well on an AR15, but not at all on an AR10.