Greg taking CS as an example I picked up one from Bill Hughes cheap yes you cannot turn the compression screw
You cannot get the engine apart no QC at $48 bucks apiece to buy 2 or more and hope you can get a good one is insane a real crap shoot a few folks have gotten ones that are OK. They really have to review their standards and do it right
if they were consistant no one would mine spending an other 10 bucks they can not even get a screw in straight and they are badly made besides

If they did this they would get a piece of the market martin