I use my camelback when I go mountian biking, although I have 2 bottles on my bike. If im in the woods for the day I know Im not going to ride past a store where I can pick up some extra fluid. On the road is a different story, I dont use it.
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2010 Kestrel RT900SL, 800k carbon, chorus/record, speedplay, zonda
2000 litespeed Unicoi Ti, XTR,XT, Campy crank, time atac, carbon forks