Features:The chuck can hold the drill bit tightly and sturdy,not easy to loose.Durable and has long service life,suitable for long time work.Easy to install and disassemble,more convenient and labor-saving.Large range of clamp size which range from 2~13mm,suitable for many kinds of drill bit.Keyless and self-tighten type design is more in accordance with human engineering. Specification:Diameter:43mm/1.69inLength:58mm/2.28in (3-5mm tolerance)Connection Size:1/2-20UNFClamp Range:2 ~ 13mm / 0.04 ~ 0.51inPackage List:1 x Drill Chuck.Note:Before purchase, it is necessary to verify whether the connecting thread of your electric drill is 1/2-20UNF. (1/2 - 20 is the definition of thread specification. Specification: 1/2; number of threads (T): 20. UNF, UN is the standard code of inch thread, and F is fine thread).