4 mm, Material Stainless Steel, Finish Plain, Material Grade/Class 18-8, Tensile Strength 150,000 psi, Ring Type E-Style Retaining Ring, Material Quality Standards DIN 1.4122.3 mm, Fits Shaft Diameter 13 mm, For Bore Diameter Not Applicable, Fits Groove Diameter 12 mm, Fits Groove Width 1.7 mm, Clearance Diameter 23.