Stark Varg MX Rear hand brake master cylinder (Formula)

The Formula master cylinder is the hydraulic end of the rear handbrake, turning lever effort into pressure in the line running back to the rear caliper. It is the Formula-supplied version rather than the Brembo one; Stark lists both, plus a kit for converting between them, so the specification already on the bike decides which fits. Part number SMX1-BR-RWH-02.