This set of drill chuck keys is made from sturdy steel and coated with durable plastic and fits a variety of drill chuck sizes. Specifications: 610 mm size: Guide diameter: 6 mm Gear diameter: 12.5 mm Number of teeth: 11 Compatible with: 1.510 mm drill chucks 13 mm size: Guide diameter: 6 mm Gear diameter: 17.5 mm Number of teeth: 12 Compatible with: 1.513 mm drill chucks 16 mm size: Guide diameter: 8 mm Gear diameter: 21.5 mm Number of teeth: 11 Compatible with: 316 mm drill chucks These chuck keys are suitable for locking and releasing drill bits in keyed chucks and are compatible with most electric drills and hammer drills. Package includes: 1 6 mm chuck key 1 10 mm chuck key 1 13 mm chuck key 1 16 mm chuck key