Keyless Hand Drill Chuck 1/2‑20UNF Mount 2~13mm Self Tighten Drill Chuck for Multiple Purposes 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/1.69in Length:58mm/2.28in (3-5mm tolerance) Connection Size:1/2-20UNF Clamp Range:2 ~ 13mm / 0.04 ~ 0.51in Package 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).