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Bi-Flex is a system developed by Boreal to improve the forward and lateral flexibility of mountain boots around the ankle area. Bi-Flex greatly enhances both the walking comfort and freedom of movement when climbing.

Mountain boots with uppers made from stiff materials can restrict the natural articulation of the ankle joint causing discomfort when walking and restricting the freedom of movement when climbing. 

Bi-Flex eliminates this problem by carefully positioning panels of soft pliable materials in specific areas of the upper. These soft compressible panels act like hinges to allow the natural articulation of the ankle in both the lateral and fore/aft directions. Hard incompressible components such as lace eyelets are either made from soft textile materials instead or repositioned so as to not cause pressure points or impede articulation. Bi-Flex greatly enhancing the ergonomics and comfort of high ankle mountain boots.

XTP Footbed

The Extreme Thermal Protection footbed has superior thermal insulation performance to help protect against extreme cold. XTP is used on our Mountaineering and Expedition boots.

The XTP (extreme thermal protection) is a special footbed with superior thermal insulation. The XTP footbed is made from a combination of a highly isolative felt material and a memory foam layer for superb underfoot comfort. XTP can be found in our Expedition and Mountaineering boots where it helps to protect against extreme cold.

Strap Tongue System

STS is a three piece tongue system which uses tabs to allow the tongue to be repositioned. Use STS to reposition the tongue to suit the shape of your lower leg for a personalized and more comfortable fit.

STS (Strap Tongue System) is a three-piece tongue construction which allows the user to reposition the different layers of the tongue using strap pads. The padded layers of the tongue can be repositioned and easily adjusted to best suit the morphology of the lower leg. This extra personalized adjustment can greatly improve the security of fit around the ankle area improving comfort and minimizing excessive heel lift.

Thermal Layer System

A thermal insulation system using Thinsulate® to completely surround the foot with no cold spots. The Thinsulate® lining is fixed in place with minimal use of adhesives to maximize loft. The base of the boot is uniquely insulated with triple Thinsulate® to minimize heat loss through the sole unit.

TLS is a thermal insulation lining system which uses layers of Thinsulate® to completely surround the foot without cold spots. The Thinsulate® lining is fixed in place with minimal use of adhesives to maximize the loft and warmth of the lining. The floor of the boot is also insulated with a triple Thinsulate® layer to insulate the floor of the boot from conductive heat loss to the ground, especially important when crampons are fitted. This full Thinsulate® lining which extends underfoot gives Boreal mountain boots a significant warmth advantage.

Heel Fit System
The Heel Fit System (HFS) consists of anatomically sculpted pieces of foam padding which hold the heel comfortably and securely in place to avoid unwanted movement.

Trekking boots require a snug fit around the heel area to prevent unwanted movement which can lead to excessive friction and blisters. HFS is a system of anatomically shaped high quality foam padding which helps to comfortably hold the heel securely whilst accommodating different heel shapes.

Ref. 47376 ARWA WMNS
Arwa Wmns

Arwa Women´s is an alpine mountaineering boot made with the very best modern materials and a fit honed by extensive testing with a team of leading alpinists. The result is more precision, more warmth, better comfort and far less weight than you would have thought possible. Arwa is like a traditional mountain boot which has been on a diet. Excess weight has been lost leaving a leaner and more athletic mountain boot which will take you faster and further. A perfect choice for ice/mixed climbing and general alpinism.

Product Info
  • UPPERS: Waterproof and reinforced one piece Dynatec with Lorica. Bi-Flex system for superior flexion and comfort. Three-piece adjustable Strap Tongue System (STS). Neoprene closure for thermal insulation. HFS padded heel system for a perfect fit. Rubber rand for protection

  • LINING: Boreal Dry-Line® for absolute waterproofness and superior breathability. Full internal single layer Thinsulate® lining for thermal protection

  • MIDSOLE: Boreal PBG-680 with lateral reinforcements for torsion control. Unique triple layer Thinsulate® thermal protection

  • SOLE: Vibram Teton. Rubber sole with dual density, shock absorbing EVA and PU. TPU heel and toe piece for automatic crampons

  • USAGE: Very cold conditions. Alpine climbing. Technical ice and mixed climbing
  • WEIGHT: 1695 grs./pair (size 4 UK)


  • The upper is constructed entirely from lightweight synthetic textiles and has a full Thinsulate™ lining which even extends under the foot providing great warmth with no cold spots. Our unique Dry-Line® waterproof breathable lining guarantees to keep your feet dry and has superior water vapour transmission performance. The innovative Bi-Flex system allows the ankle to move freely greatly enhancing walking comfort and freedom of movement when climbing and a three-layer tongue provides plenty of padding against pressure points and adds some useful adjustment. 

  • Arwa is fully compatible with automatic crampons and uses dual density crampon lugs, hard at the rear for a secure fit and soft at the front for reducing vibration when front pointing on bullet hard ice.  The advanced carbon composite midsole is rigid, yet incredibly lightweight and ample underfoot cushioning is provided by dual density shock absorbing PU and EVA layers. Finally, our choice of a deeply lugged Vibram® Teton outsole will help keep you upright on the approach.