Love my Deuter SL Bike backpack. it's women & bike specific (so it's not so long as to bump on your helmet). It has an expansion zip for when you need to carry more. It has a great back which keeps you cool in the summer. Very comfortable & never seems to look worn let alone worn out. It has a special strap to hold your helmet when you are off the bike - also it has a waterproof cover & will take a bladder. Finally - the waist strap has little zips to put things in you need access to quickly. It's not cheap - but it has lasted & lasted - if it ever wears out I will definitely buy another!