FWIW- the modular rest sold by CSUSA is made by Best Tools. I have used them for years and love them. I can only think of once or twice they have ever loosened, not what I consider a problem. We could get into the whole round vs. flat rool rests debate again, but all I'll say is that these work great for me.
I originally bought the set straight from CSUSA bought added a few pieces straight from Best Tools this past summer in Lex. Great people to talk to. Small company but growing and expanding their product line.