From memory there is no RBA for the Crown 3, they never planned to make one last i heard, and pretty sure the original one doesnt fit in it...ill stand corrected if anyone has better info.
I only ever had the original Crown and RBA, and i famously rage posted them back to the actual head of Uwells desk, nice man, refunded my money AND sent me an entire new Crown and RBA kit, which i piffed to another vaper on my home forum - its since become a running joke as it has been passed around a few times because no one could live with it - only the other day i wondered aloud on the forum who currently had it...
The Crown 1 had a huge issue with stock coils, it was like the lottery finding a batch of coils that would last more than 2/3 days, Uwell never instituted batch tracking and couldnt recall the bad ones, and they went through several iterations of them with still varying degreess of success. This same issue, continually revised coils, still pervaded the Crown 2 and 3...
The original RBA was just fiddly and underwhelming - s wicking anyone? sheesh, i lasted exactly one tank, and a record 4 builds for a new tank on it before the whole lot went back to whence it came...still equal worst tank ive ever had...along with the famous Subleak Spitty (Subtank Mini) - 1st tank i ever owned....
Update:
From here:
Crown RBA Coil
Comes this line:
- Only meant for use with an authentic Uwell Crown subtank