Flat Washer USS Through Hardened Steel Finish Zinc Plated with Yellow Dichromate Fits Bolt Sizes 5/8 In Inside Dia 11/16 In Outside Dia 1 3/4 In Thickness 0.108 to 0.160 In Rockwell Hardness Rc 38-45 Load Distributing For Use With Grade 8 Fastener Meets/Exceeds ASME/ANSI B 18.22 and ASTM F436 Refills 6PE88 Package Quantity 1000