Ski backpacks are special bags from the category of sport backpacks. They are designed for both skiing and snowboarding, generally for winter sports. They feature ergonomic shaping, soft padding, usually functional materials that are waterproof and breathable, and the presence of ski or snowboard straps. The more advanced ones also have integrated water bags or an anti-snow-slide-system system that releases airbags that can create an air bubble to protect against injuries. Generally speaking the backpacks that are more expensive justify their price tag by high functionality and usability in extreme conditions. Their equipment, of course, differs from model to model so choose carefully.