Russell brake residual valves eliminate spongy - pedal feel by retaining brake - line pressure and keeping your pedal firm. The valve stops brake fluid from draining back into the master cylinder this keeps your caliper pistons and brake shoes from fully retracting so your brake system stays primed without brake drag. The result is a firmer pedal that engages quicker and provides increased braking response. These residual valves are polished for great looks and available in 2 psi for disc brakes 10 psi for drum brakes drums require more pressure to compensate for return spring tension.