I think there's about a dozen or more kinds now! lol.
LR is lower resistance - usually 1.5 to 1.8 ohm depending on who you get 'em from. Joye 510s are 2.2 - 2.3 ohm.
I think most of the VapeStacks shipped with 3.3 ohm SLBs. IMO they're great at 5v, but at 3.7, not so much.
Hoog has said he's...