What Our Gearhead® Experts Are Saying: "I’ve got low arches and struggled with foot movement in my boots. These insoles really dialed in the fit. Plus, they’re warm and don’t hold moisture like my old liners did."For riders and skiers with lower arches, the BootDoc Thermo X offers the perfect balance of winter-ready warmth and anatomical support. Crafted with BootDoc’s flatter profile, it brings structure to low-volume feet without feeling bulky or overbuilt. A merino wool top layer ensures temperature and moisture are regulated inside your boots, even on the coldest or sweatiest days. Subtle stabilization at the rearfoot and heel reduces movement, improves fit, and keeps your feet feeling fresh lap after lap.