Almost everything here is decided by trade size and material rather than by looks. A 1/2 inch liquid-tight connector does not fit 3/4 inch conduit, an EMT compression fitting and a rigid compression fitting are not interchangeable, and a weatherproof box needs its matching in-use cover to keep the assembly rated. Where an item is listed by UL or cUL and what the listing covers also matters, because inspectors check it.
This group covers conduit bodies, liquid-tight and EMT connectors, couplings, weatherproof and fan boxes, floor boxes, raceway supports and the covers and gaskets that complete each assembly. Trade sizes run from 1/2 inch through 4 inch, in steel, malleable iron, aluminum and PVC.
