Metric Heavy Duty Internal Ring System of Measurement Metric Location Style Internal Thickness 1.5 mm Fits Shaft Diameter Not Applicable For Bore Diameter 20 mm Fits Groove Diameter 21 mm Fits Groove Width 1.6 mm Fits Groove Depth 0.5 mm Free Inside Diameter Not Applicable Free Outside Diameter 21.5 mm Clearance Diameter Not Applicable Material Spring Steel Material Grade/Class 1060-1090 Tensile Strength Not Applicable Ring Type Heavy Duty Internal Ring