The two failure modes in the field are mismatched thread types and mismatched materials. Rigid, IMC and EMT do not share fittings, and a die-cast zinc connector and a malleable iron connector behave very differently under vibration and corrosion. Liquid-tight connectors come in straight, 45 and 90 degree forms, insulated and uninsulated, and the one you need depends on where the flex lands relative to the enclosure.
We stock combination and C-type conduit bodies, set-screw and compression connectors, liquid-tight connectors in straight and angled forms, rigid couplings and nipples, in trade sizes from 3/8 inch to 4 inch. Listings and material are listed per item.