Zinc Plated Steel Shaft Collar, Set Screw Collar Style, Standard Dimension Type, 1/2 in Bore Dia./ OUTSIDE DIAMETER: 1.000 INCHES NOMINAL THICKNESS: 0.438 INCHES NOMINAL BORE DIAMETER: 0.5000 INCHES NOMINAL END ITEM IDENTIFICATION: SPECIAL AIRCRAFT AND ENGINE TOOL AND SUPPORT EQUIPMENT MATERIAL: STEEL STYLE DESIGNATOR: A1 PLAIN ROUND