Nominal Washer Size 5/8" (0.625") Inside Diameter Max 0.663" Outside Diameter Max 1.070" Thickness Max 0.050" Type 410 Stainless Steel is the general purpose corrosion and heat resisting chromium stainless steel. It is hardened by thermal treatment to a wide range of mechanical properties. This grade is always Magnetic. External Tooth Lock Washers are a hardened curcular washer that have twisted prongs called "teeth" which extend out from the outer edge of the washers. These lock washers offer the greatest locking efficiency since the teeth are on the largest radius and provide greater torsional resistance. External tooth lock washers are the most preferable of all types of tooth style lock washers.