I've been using this pack as a spare while my Millet pack is being repaired after stitching blew out. I'm a 38" chest and using the M/L. I feel like I'm right in between sizes as the S/M fits best across the chest, but is difficult to reach into the safety box while the M/L is a little loose on me unless I use one of the waist/sternum buckles. Obviously using a suit or race-inspired top that is loaded up makes things fit a bit better.
As a race pack you're well able to get all of your required gear in the pack assuming you're using race-category gear. An Arva Carbon Compact 2.40 probe and Ultra shovel fit easily in the M/L with enough room for a pair of Mezallama pants and jacket with room to spare. Additionally there is a small sleeve for a smaller hydration bladder and a mesh zippered pocket for small essentials. Down below in the safety box, you'd easily be able to fit a pair of race/lightweight touring crampons with room to spare for gloves or skins. A beefier pair of technical crampons will also easily fit, likely with some spare room.
The ski carry system works well with a caveat (see below) and the horizontal orientation of the bottom ring makes it easy to thread tails when breathing hard and mentally frazzled. I may have preferred a wider or stiffer piece of material for the loop but that is just my preference. The exterior bottom of the pack has a bungee loop stitched into a square of fabric that creates an open pocket and a small loop sewn in towards the body that is ostensibly for a partner tow (no tow cord is supplied with the pack). In the "I'm not sure what purpose this serves" department the function of the former fabric pocket and bungee loop escapes me. Please feel free to clarify and mock my cluelessness if the purpose is obvious. Finally, partner ski carry, basic single axe carry point, and an external port on the shoulder for hydration bladder use round out the packs features.
The pack's strengths come from Ultimate Direction's pedigree as a functional vest designer. Using soft flasks, this pack makes hydration and eating a breeze when temperatures allow for flasks to be outside of the suit. The often wasted real estate of your shoulder straps is jam-packed with functional space on this vest/pack (and also a safety whistle to meet ISMF requirements). Aforementioned adequate space inside let's you carry what you need for a day without too much hassle.
On the downsides there are a couple of issues that are just straight-up perplexing given the attention to detail on the other aspects of the pack. I'd love for someone to point out where I'm just misinformed or clueless if any of these points are off-base. The bungee hook for the ski carry system seems to be unnecessarily long to the point where the skis disconcertingly flop around. This is easy to resolve by just tying a knot in the bungee cord which reduces the available length (and therefore increases tension) and provides a more secure carry. The axe/tool carry loop on the bottom is also oddly long and leaves an axe flopping around on the outside of the pack. Maybe this is to facilitate stowing two tools/axes? However if only carrying one, an overhand knot in the loop at the base of the stitching reduces the length of the loop and reduces the amount of flopping to a more reasonable level.
My personal gripe is that the sternum/waist buckles have small magnets in them in an attempt to make it easy to close the buckles with gloves on. I don't find this to really provide much help and I haven't found snapping a buckle with gloves on to be overly difficult on other packs. The real problem here though is that magnets emit electro-magnetic fields. Electro-magnetic emissions potentially can cause interference with avy beacons. Given that even headlamps have been reported to affect beacon transceiver functions, I find it hard to believe that these magnets would not also potentially cause interference (http://www.mammutavalanchesafety.com/2014/10/electrical-interference.html). I've communicated this concern to UD and hopefully they will get an definitive answer, but for the time being if using a beacon with this pack it may be caveat emptor.
So overall great design and very functional for racing, but a point off for a couple of odd design choices that leave at least me scratching my head.
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