The AK47, AK47-X, AK57 and AK70 come in three sizes, based on back length (see table and diagram below).

The AK37, AK37-XAX45, AX50, RK40 and RK50 come in two sizes, R (regular) and L (long) (see table and diagram below)

The AK27AX30, AX35, AX40, RK20 and RK30 come in one back length only, which is equivalent to size R.

Size Back length (cm) Typical height range
1 45 160 - 170 cm
R 48 155 - 175 cm
2 50 170 - 180 cm
L 55 175 - 185 cm
3 60 180 - 190 cm

Size 1 is optimised for women, but fits small men also.


The height range given for each back length is only a guideline and may not be right for your particular proportions. We always recommend trying on our rucksacks before you make your final choice.

Typically, the hip-belt should wrap around the middle of the pelvis, so that the hips are able to share the overall load (see diagram). But you may wear your rucksack differently, and this will also affect your choice of size. For example, some climbers carry their rucksack “high” – in other words, around their waist and thus above the pelvis – and may prefer a rucksack with a shorter back length.