Flat Washer, 5/8, Pk50/ CROSS-SECTIONAL SHAPE STYLE: 1 RECTANGULAR HOLE DIAMETER: 0.688 INCHES NOMINAL PERIPHERAL SHAPE STYLE: 1 ROUND CENTER HOLE SHAPE STYLE: 1 ROUND THICKNESS: 0.122 INCHES MINIMUM AND 0.177 INCHES MAXIMUM OVERALL DIAMETER: 1.313 INCHES NOMINAL HARDNESS RATING: 26.0 ROCKWELL C MINIMUM AND 45.0 ROCKWELL C MAXIMUM SPECIAL FEATURES: USED FOR STRUCTURAL LEVELING; MEETS/EXCEEDS A325 AND A490 BOLTS; FINISH: HOT DIPPED GALVANIZED MATERIAL: STEEL OVERALL