Right. Space saving is the best thing about them, including saving the space needed to switch between operating them. That said, I sometimes find that turning one of the knobs affects the other one, and that's no good. On my Intrepid, the front rise/tilt concentric knobs are only ok. The regular knobs are all easier to use, even if they're thinner. Ideally, controls should be smooth to operate with progressive locking. For me, that's more important than space saving, but maybe if concentric knobs are made properly, they'll work fine. On my P2, tilt and rise are concentric..but they're big knobs and using one doesn't interfere with the other.