I got the Centech 4-piece combination square set HF#92471 for around 6-7 bucks. I think it was on sale for $6, a buck off the regular price. Having a decent Stanley Comb. Square, I wanted a protractor and centerfinder attachment. I figured for $6, how bad can it be?

Came in a wooden case which it turns out was the best part.
The fit and finish was awful. the metal was rough, the paint rough and peeling and the parts did not slide well at all. I guess the square and centerfinder move OK (locking screw was a little rough feeling), but the protractor took a superhuman effort to move (rotate) and the scale was all but unreadable, the scale was on one piece and the indicator marks on the other moving piece but they were on slightly different, non-parallel planes so the faint markings (hard to read except at a perfect incident light angle) required two perfect incident light angles to read. I.e. you can't read both at the same time. Rule Scale was stamped, not engraved, kind of low quality. At least the markings were in the correct place.
I kept the rule with the centerfinder and tossed the protractor and the square handle. I did not even bother to check if the square was at 90°.

The parts do interchange with other combination squares out there... the rules being simlar withthe locking groove in the same place.

The best part was the box, I eventually bought a used Starrett 4-piece set for around $60 (current new price around $140) and I keep it in the box!

There's no comparison to the Starrett set, which has impeccable finish and everything slides smoothly and very easy to read the engraved scales (protractor and rule). Even though the set is probably 30+ years old.