I started out with just some water and a cell phone for rides through the neighborhood. Then I needed a small bag for keys, id, etc. Then I needed a little bigger bag for repair stuff (until then I was happily ignorant about the possibility of a breakdown!). Now I have a much bigger trunk bag on a rack, which I think looks kinda silly. But for a long time it seemed like every time I needed something, I didn't have it with me. So I have the usual repair stuff (I'm a new tube girl, not a patch-it girl), snacks, more water than I need, keys, id, money, phone, extra gloves (I hate it when my gloves get wet from sweat!), a jacket or something if the weather is questionable, Tylenol, chap stick (no lipstick), and always a hat for when I take off my helmet and my sweaty, wet hair is stuck to my head!