From winter ascents of the Eiger to 7000-meter climbs in the Himalayas, Boreal's Siula Mountaineering Boot delivers the performance necessary when climbing in high and cold alpine environments. In terms of design, the Siula was built to sit between Boreal's Everest-grade G1 Expe boot and its light-and-fast climber, the G1 Lite, making the Siula a great choice for most alpine endeavors. Its triple-layer construction consists of an integrated outer gaiter, outer boot, and inner boot for dependable warmth, resistance to wear, and all-season versatility.The outer boot's outermost layer is composed of two materials, both of which are breathable and highly resistant to wear. The outer gaiter is secured via the waterproof Tizip closure. Six millimeters of EVA foam acts as an insulating layer, which is backed by a waterproof and breathable layer of Cordura nylon for added protection against moisture. Boreal even added a light, but durable TPU rand along the outside gaiter for added protection against rock, ice, snow, and crampon bails. The inner boot features triple-layer Thinsulate insulation to help eliminate cold spots and is supported by a heat-reflective layer of aluminum film to direct radiant heat back towards the foot. The sole of the inner bootie features a textured TPU surface to reduce slipping for a more secure and reliable climbing feel.When it comes to climbing, the Siula is tough to beat. The stiff, supportive midsole offers a secure and stable platform to climb with, but is also light thanks to a carbon composite material. Boreal then weaved in layers of shock-absorbing PU and EVA to help absorb vibration when toeing in on sections of bulletproof blue ice. For ease of use on the mountain, Boreal added toe and heel welts to the Siula, making it compatible with automatic crampons. The whole boot is built on an aggressively lugged Vibram Teton sole for a sure-footed feel when climbing without crampons.