Great small to midsize hydration back with room for the essentials just like the description says. This pack (like most/all Dakine packs) uses a Hydrapak reservoir with a quick disconnect at the bottom so you do not have to unthread the drinking tube to fill up the reservoir. When filled up to its 100oz capacity, there was still enough room for a shell jacket (Alpha LT in XL), a multitool, cell phone, keys, and some snacks. I haven't tried out the helmet carry, but it looks like it will work as advertised. The shoulder straps are comfortable and the waist belt keeps it from bouncing around too much when it gets rough.