I’ve run with a variety of different hydration systems, from handhelds to waistbelts to vests and packs. When it comes to hydration, I tend to be a minimalist; particularly in training, I rarely carry much of anything, except on the longest efforts. But for long training runs of 25+ miles, or unsupported or minimally-supported races, I’ve had good results with both the Ultimate Direction AK vest and the Orange Mud HydraQuiver. Neither of these have enough storage for a long day hike, though. Recently, on a family hike through Black Creek Preserve in Esopus, I was able to test out the Ultimate Direction Fastpack 20.
The Fastpack 20 is a day hiking pack that is inspired by UD's Signature Series of running vests (the AK/SJ/PB vests that are widely seen on the ultra running circuit). As with all the vests in that series, the water bottles are located in front, on each shoulder strap, which makes for easy access and excellent stability. Also with the vests, the shoulder straps are secured by two adjustable sternum straps, which I prefer when hiking (though they can sometimes annoy me when running). The shoulder straps are nicely padded and quite comfortable, though I did find the ride a little low on my back.
The pack itself is basically one big pocket with about 20 liters of storage (hence the "Fastpack 20" moniker). There are mesh pockets on either side which are fairly spacious for additional items, as well as built-in lashes for trekking poles, which is very useful. One cool feature is that the main compartment has no zippered closure or flap over the top; basically, the upper part of the compartment rolls over on itself and secures to the sides with clips. I'm not sure why I liked this so much, but I found it extremely cool. I think I just like the fact that there are so few extraneous/moving parts. You can really cinch the pack down if you're traveling light; it compresses to about 15 liters if you want. This top rollover compartment is waterproof, and the rest of the pack is water-resistant.
Much like the Signature Series of vests, the Fastpack is very streamlined; it's large enough for everything you would need for a long day on the trails, but not so large as to be cumbersome or to invite over-packing. Having the water bottles on the shoulder straps can take a little getting used to if you're not familiar with it, but having run in UD products before, I appreciate the convenience of easy access to water. The fit of the back panel is a change from the vests, and on first wearing was not as flexible as I'd like, but I suspect that will improve as the pack breaks in a little bit. All in all, the Fastpack is an excellent choice for day hikes or even a weekend if you're traveling light.