I will say, If you defy the listing and directly glue the Carflex in an FS box, continue your defiance and use primer.
I know from "spaflex", the white equivalent, Pool installers will tell you the primer is as important as the cement.
Most inspectors I know would question that installation tho. As "crappy" as the Carlon connector might be, it is the only listed solution.
It should be noted that Carlon does say you can direct glue ENT in their boxes and fittings. I was surprised when I read that in light of the Carflex thing.
