evo.com | Fox Racing Bike Helmets > Protect your main asset with the Fox Racing Mainframe Bike Helmet. Built for the next generation of riders, the youth-specific Mainframe Helmet offers the same proven safety features as the adult version - an extended coverage design, MIPS(TM) impact protection technology, and a lightweight, breathable in-mold EPS construction. Optimized Venting with Channeled, In-Molded EPS MIPS(TM) Impact Protection System Reduces rotational forces in a crash. In-Molded EPS Youth (One Size) 19 - 20.5" Head Circumference (6 - 6 1/2" Hat Size) EPS, PC, PA, Polyester | Kid's Fox Racing Mainframe MIPS Bike Helmet 2025 - in Yellow | Polyester