I have built on these. Not bad at all considering the price. it does have a threaded prep for an upper tension screw, through its not the correct thread…its to small for the available 1/4-28 thread. No idea why but you can drill and tap the correct one which I have done and it works fine.
Separating from the stigma of “oh those are so cheap”as the snobs would say, I would put my build on the same range as DD and WC and feel comfortable with the performance.
Bought several a while back. Finish and machining quality are on par for what you'd expect out of a $30 lower.
The upper and lower receivers were not even close to having the same finish, not in color or texture, two completely different types of cheap anodization, and plenty of flaws in the machining that isn't hard to tell their tooling isn't the best. Out if the three I got none mated together very well, but all plenty well enough to make a functional rifle.
Really it's not a super good deal, another $50 could probably get you a basic Aero set that's gonna have a much nicer fit and finish. They're just a cheap receiver set for a budget build and there's nothing wrong with that.