HLS-8 HEICO Fastening Systems HEICO-LOCK Washers , Manufacturer Part#: HLS-8 , Manufacturer: HEICO Fastening Systems , Brand: HEICO-LOCK Washers , UOM (Inch or Metric): Metric , Material: Steel , Finish: Zinc-Flake Coated , Bolt Size: 5/16 Inch UNC (M8) , Inside Diameter: 0.340 Inch (8.60mm) , Outside Diameter: 0.530 Inch (13.50mm)