I like to have all that I need when out on a bike. If not wearing a rucksack, I seem to need more space than the shirt pockets and a saddle bag allow. This bag fits neatly on the frame, doesn't wobble about - and is reassuringly in line of sight if you might be anxious about losing things like money, phone, camera. Your knees won't catch it as you pedal. I haven't exposed it to rain, yet, but would recommend as a way of getting a bit more storage.