Mammut MTR 201 10+2
Here's what other sites are saying:
The MTR 201 Hydration Pack is Mammut's lightest trail running pack for the runners who don't want anything holding them back. Its Contact BaseFit suspension system provides a comfortable, secure, and stable ride while VenTech materials cover the back panel and shoulder straps to breathe and dry quickly. A zipper allows you to expand this 10-liter pack to 12 liters when you need an extra layer in chilly temps. This pack also has a separate hydration compartment for your reservoir (not included) so your layers don't get wet. Pockets include a three-compartment organizer at the shoulder strap to separate your sunglasses from your lip balm and energy bars, a front zippered pocket to secure your car keys, two mesh side pockets for water bottles and garbage, another bottle holder on the shoulder strap, and an elastic front bungee cord that quickly stows layers away once the day warms up. Mammut also added a carrier for hiking poles and reflective prints to keep you visible in low light.