Box Two™ Brake Post Extenders are the perfect solution for those riders in need of extra brake pad adjustment without switching frame sizes. CNC-machined from 6061-T6 aluminum, Box Two™ Brake Post Extenders easily mount to any frame’s existing cantilever brake bosses and provide an additional 16 mm of brake arm positioning. Typically, they are most useful when a rider transitions from one wheel size to the next (i.e. 451 to 406). Depending on your application, they can be mounted in either one of two positions -- above the frame's v-brake mounts, or below.