Geared chuck: 1.5 - 13mm; 1/2" - 20 UNF; SDS-plus adapter with 1/2" - 20 UNF male thread, chuck key For use on rotary hammers with SDS-Plus holder; for clamping cylindrical drill bits, tools with cylindrical shaft Drills through using locking screw for clockwise and anti-clockwise operating machines Constructed with all metal for supreme durability | Please Note: The chuck can NOT be used counterclockwise! Classic keyed 3-jaw design securely holds a wide range of twist drills and step drill bits with 1/16" to 1/2" shank