S2 tool steel. Blast finish steel bits provide a firm hold to the fastener. Highly resistant to wear and tear for long life. 1/4 In. hex shank fits all standard bit holders and hand-held drivers. Size: #10 Spanner Security Length: 1" Shank Diameter: 1/4" Hex Warning: This product can expose you to chemicals including lead which is known to the State of California to cause cancer. For more information go to www.P65Warnings.ca.gov -