Sealing locknuts are intended for RGS/IMC. They are intended to go on the outside of the enclosure so the "seal" is on the exterior side of enclosure.
A "raintight" compression fitting will have a sealing washer that goes on the exterior side of the enclosure.
That is how these are listed, practicality of use and how long they hold up is a different story. Sealing washer on most raintight compression fittings I ever used are crap. I mostly quit using them because if you come back in a year or two you will find it has deteriorated from sunlight and the fitting isn't even seated tight at all - worse seal than a set screw fitting would have made:slaphead:
