Stef...
If you're talking about an "in-line" moisture trap, then you will have to cut the braided air hose and fit it in. I have one from Paasche. The two ends of the trap fits very tightly into the airbrush's airhose so I didn't even have to put on the two locking screws. Also, be sure to put it in as close to the airbrush end as possible.
I live on the coast of the Gulf of Mexico and it is very humid so I have a moisture trap at the end of the compressor but still need an inline one. Even then, during the dryer winter months when working outdoors, I still see water condensing in the inline trap. That's why I built a spray booth recently to move my painting indoors.