La Sportiva Ski Boots Size Chart Fast transitions, light on-foot, and built for aggressive descents; the Sideral 2.1 is the all-around ski boot designed to meet the requirements of modern ski mountaineering. This boot lets you conquer the peaks and enjoy the ride down. Features: - Fast Lock System(TM) consists of the unique Vertebra Technology(TM) with the Cam Closure System(TM) allowing for a lightning fast transition between ski and walk modes - Removable PU Warmsole(TM) insole makes the Sideral 2.1 one of the warmest 2-buckle boots on the market - Weight: 2.1 lbs 8.50 oz (1150g) (half pair, size 27) - Grilamid shell - PA12 Polyamide / Nylon cuff - Vertebra: Carbon reinforced polymer - PA12 nylon and carbon fiber - Pebax tongue - S Boot Liner - Forward lean: 3 positions (12? / 14? / 16?) - Fast Lock System(TM) with Vertebra Technology(TM)/ Pegasus Buckle(R) with optional power strap - Range of motion: 68deg - Flex: 90 - Compatible with all "tech-style," Trab TR2, and AT touring bindings - Sole: La Sportiva LazerGrip(TM) by Davos