Low profie/haircut - the black Reo. Anything fits it. Copper one on the right. Nah! To work they have to fit in the catchcup and there's a thread if you prefer those.
http://www.e-cigarette-forum.com/forum/reos-mods/377836-reo-compatible-rbas.html
I liked RM2's for easy building. I have rhino claws so small atties are a bit fiddly for me, but Cyclones are good too by all accounts. FB - Filthy Beast, uses those a lot.
T
the RM2 and Cyclone have very similar flavor profiles, the Cyclone is a little smaller air chamber so IMHO it's slightly better. Because of the spread posts and ceramic deck the RM2 is much easier to build on and I highly recommend it for people new to building. Only time I don't recommend it, is for those already building and doing low sub ohm dual coils and lung hitting or those who have a reaction to brass or plating. The Cyclone is all stainless steel, the RM2 is plated brass.
Here's a shot that shows the difference, LP on the left. The LP can run any rba the regular like you borrowed can only use RBAs that are 14mm in diameter or smaller.
