There are quite a few things that don't make sense with plastic raceways.
You can glue Smurf tube into a RNC connector but you can't glue Carflex (Flex nonmetallic) into one.
That is strange to me because you can glue the white kind (spaflex) into an identical plumbing connector and it is rated the same as sch40. (well over 100PSI)
I think that is simply because they sell the LFNC connectors for about 10x as much and a smurf connector is about the same.
... but I may just be cynical.
