For day-long rides on a road bike, this bag is almost perfect. I also own the Topeak Aero Wedge pack in medium size, and for me the medium size is just a bit too small to carry everything you need for a good day's ride -- tire levers, CO2 inflator and valve, spare tube, tire boot, car keys, cell phone, cash and perhaps a rain jacket. The large size of the same pack carries all of this stuff comfortably yet is almost unnoticeably bigger and certainly not intrusive.Very satisfied.