M4 x 9mm OD DIN 125 Low Carbon Zinc Finish Steel Type A General Purpose Flat Washer / CROSS-SECTIONAL SHAPE STYLE: 1 RECTANGULAR HOLE DIAMETER: 4.0 MILLIMETERS MINIMUM PERIPHERAL SHAPE STYLE: 1 ROUND CENTER HOLE SHAPE STYLE: 1 ROUND THICKNESS: 0.8 MILLIMETERS NOMINAL OVERALL DIAMETER: 9.0 MILLIMETERS NOMINAL MATERIAL: STEEL OVERALL SURFACE TREATMENT: ZINC OVERALL