Finish Line's DOT 5.1 Brake Fluid is a high-quality fluid for maximum life and braking power. It exceeds the most stringent 5.1 specs and is compatible/mixable with all DOT 3, 4 or 5.1 spec'd systems. It also features a super-low viscosity to yield superior lever response and pad retraction. Plus, it won't foam up even on long, challenging downhills.