I don't think many had a good experience (and neither did I) which the stock RBA or the Kanger OCC heads
charlie1465. Besides everything else gives you a better vape, the RBA/OCC option, the chimney (its called a bridge) likes to pull off of the RBA/OCC when you unscrew the drip tip holder (its called a key) to remove the tank. You could remove the o-ring off of the key if you would like, as it won't leak.
There is also a SXK Billet Box thread too. It's kind of new (only 4 pages now) and you can get lots of info there.
SXK Billet box...