The mission was to combine the light weight and nimble fit of a single boot with the insulation and protection of a double boot. And - claims Canadian brand Arc'teryx - it was years in the making. So, if you're an ice or mixed climber and mountaineering around the 5,000m mark is your passion, the Acrux AR boot is aimed squarely at you. Please feel suitably excited.
The first thing to notice is the lack of seams here, giving the boot a pure and purposeful look. The construction is utterly solid too, with the huge rand melting effortlessly into the Gore-Tex gaiter, which makes up the Acrux's upper half.
The sole, dubbed the Vibram AR, was built specifically for the Acrux and is fearsomely grippy in both appearance and performance, combining anti-slip grooves with a strong and forceful heel brake.
Slip your foot into the inner bootie and the simple brilliance of the design is driven home quickly. Adjustment inside is minimal, with a lace system and hook and loop belt seeming almost unnecessary thanks to the remarkably snug and supportive nature of that inner layer. The outer gaiter is then zipped up swiftly and firmly by an excellently robust zipping system, with a popper and pull-cord adjuster at the top. It's hard to imagine a boot which fits more closely (almost to a fault) or confidently.
The bootie is, of course, removeable for use in Alpine huts and to dry the boot overnight in between routes. However, the weather protection - it is entirely wind and waterproof and rates highly for breathability - is supreme and you're unlikely to suffer too much in this regard.
The weight rating of 980g per boot is class-leading for a double boot and - although only rated by Arc'teryx for use up to 5,000m - the warmth when in use is admirable and effective insulated socks could push that ceiling higher. Needless to say, it is B3 rated and can hold even the stiffest of crampons.
In conclusion: this is everything you'd expect from an Arc'teryx product. Innovative, ground-breaking and unquestionably capable. Compare its hefty price tag to that of its competitors and it comes off extremely well too. A pity so few people will ever need the performance levels it offers.