Alpina Sports Alaska Nordic Cross-Country Ski Boots for NNN-BC Bindings Medium flexing NNN-BC sole with great torsional rigidity provides optimal ski control while still providing flex needed for kick-and-glide skiing Thinsulate insulated waterproof-breathable Alpitex membrane lined 2.4mm leather uppers provide comfortable wrap-around support for off-track skiing Comfortable soft collar and speed lacing system ensure a comfortable and secure all-day touring fit Anatomic footbed provides a good foundation and stiff toe box eliminates toe box collapse onto to toes Designed for use with Rottefella NNN-BC bindings