After much debate on Osprey's packs for cycling, I chose the Syncro 10, and I am glad I did! I wanted Osprey because I've had amazing experiences with getting packs repaired by their warranty department. This pack is perfect for big, all-day rides. I can fit both a puffy and a windbreaker, snacks, bike light, tools/tube, cell phone/wallet/keys, and still have room for more. The 2.5 liter bladder holds more water than I ever need, and the helmet holder attachment is nifty when I need to throw the hole package in the car. I am 5'1" and the S/M is a good fit.
This review was written in the old system and had content requirements that are different than reviews written today.