The I-Flex Zone at the front of the boot provides an additional flex point on the Hawx 100. The I-Flex Zone promotes natural forefoot flexibility which in turn improves balance on the skis with optimal precision and control. The improved maneuverability makes walking even easier too. The Insole of the Hawx 100 is prewired for Thermic Boot Heaters, purchase the battery packs separately for warm and toasty feet on the slopes day in and day out. . Liner: ASY Sport Fit T2 Womens Liner, Flex Rating: 100, Cuff Alignment (Y/N): Yes, Warranty: One Year, Gender: Womens, Type of Boot: High Performance, Width: 100mm, Buckle Count/Type/Material: 4/Micro Adjustable/Magnesium, Features: I-Flex Zone, Skill Range: Advanced - Pro, Model Year: 2009, Product ID: 202771