The system's refillable with stocko air which is an awesome idea considering this can be done with a regular pump. Obviously won't reach the required pressures, but it'll help you get home if you take it for a trail ride. Obviously designed for racing thow. The Rear mech is supurbly built and shifts so crisply (whether this is due to the air powered shifting, i'm not too sure), and the shift paddles are so nice. The downside is you can only downshift one cog at a time. If you farkup in a dh run, it's always nice to dump 3 gears in one go with a standard rapidfire shifter. This is where airlines lose the 'quick-shift' war.