Shop › OBP Brake Bias Proportioning Valve (Screw Type) Image 1 of 1 OBP Brake Bias Proportioning Valve (Screw Type) £32.80 This is OBP's screw type brake bias proportioning valve with M10x1 threads. Suitable for adjusting the brake pressure. Purchase Added! This is OBP's screw type brake bias proportioning valve with M10x1 threads. Suitable for adjusting the brake pressure.