Don't worry, we won't ask you anything about your math class, we are just here to wax lyrical about the Head Formula 120 Ski Boot. This stiff and reliable alpine ski boot combines a 120 flex that drives power to your edges with minimal energy loss with a snug but comfortable 100mm last. The result is a boot that will thrive on the feet of powerful carvers, freestyle-minded pow skiers, and everyone in between.