Responsive and Durable: Polyurethane (PU) plastic shell offers premium rebound, response and long-term durability. Customizable Fit: Our Thermoformable liners adapt to your specific foot shape, making your ski boots feel like a natural extension of your body for maximum comfort. Lightweight and Durable: Aluminum buckles offer reduced weight and increased strength for efficient closure and long-term durability Race-Ready Fit: Our Junior last is designed for junior skiers seeking a precision fit Flex: 50 All-in performance for junior skiers. The Lange RSJ 50 Ski Boots bring race-inspired design to junior racers looking to push their skiing. From the responsive power of the PU shell to its anatomical foot-hugging design, the RSJ offers excellent support and power transfer for full engagement in every turn. A 50 flex is for the lightest juniors seeking a performance boot. Lange Youth RSJ 50 Ski Boot