The Jacobs Hand-Tite keyless drill chuck features a split bite jaw, which increases grip over standard bite chucks by providing more contact with the bit. The Jacobs Hand-Tite keyless drill chuck features superior gripping force: provides high mechanical advantage to convert hand tightening torque into superior bit gripping force.Hammerlock mechanism: positive locking mechanism prevents loosening in hammer and other high vibration applications. Anti-lock nut: prevents chuck from locking open. The Jacobs Hand-Tite keyless drill chuck features offers versatility: models available to fit all 10mm (3/8”) and 13mm (1/2”) variable speed corded and cordless portable drills. Precision operation: meet or exceed stringent din run-out and dimensional specifications.Ergonomic design: material and surface finish combinations result in increased comfort and performance. Rugged construction: constructed of high performance material to maximize durability and performance.