With any splices in this fitting, assume 14 AWG's, we would need a
box with at least 10 cubic inches [5 x 2 CU IN].
Does this fitting show marking with that information?
I posted this because this transition seems to require only wiring methods that include an EGC, such as MC and NM.
http://www.nachi.org/bbsystem/usrimages/v/verystrange.jpg What do you say?