2022 Atomic Redster STI 150 Ski Boots NEW! Size 24.5-The 2022 Atomic Redster STI 150 race ski boots are an incredible popular model in the Atomic race boot line. This slim shell race boot comes with a 150 flex, a narrow 93mm last, and a lace-up liner. The World Cup liner with memory fit helps the racer have the perfect fit to drive their skis as hard as they can.