HLS-20 HEICO Fastening Systems HEICO-LOCK Washers , Manufacturer Part#: HLS-20 , Manufacturer: HEICO Fastening Systems , Brand: HEICO-LOCK Washers , UOM (Inch or Metric): Metric , Material: Steel , Finish: Zinc-Flake Coated , Bolt Size: M20 , Inside Diameter: 21.40mm , Outside Diameter: 30.70mm