【Precise Collet Adaptation】The collet of the high carbon steel drill bit extender has an inner diameter of 9.7 mm (about 3/8 inch) , with tight tolerance control , it can stably clamp 3/8 inch and slightly smaller diameter bits , ensuring no slippage and high concentricity during drilling 【High Carbon Steel Structure】Practical drill extension bit holder is constructed of quality high carbon steel , precision ground and polished to provide high hardness , wear resistance , stability and endurance for long term heavy drilling work 【Easy to Install】High hardness drill extension bit comes with 2 fixing screws and hex wrenches , no need for additional tools , simply tighten the screws with the wrenches to fix the shank of the drill bit , so installation and disassembly is efficient and no hassle 【Universal Adaptability and Compatibility】Versatile bit extension is designed with a 3/8 inch hex shank , which is compatible with most of the electric drills , impact drills and other common tools , with total lengths of 11.5 cm (about 4.5 inches) and 17.8 cm (about 7 inches) , respectively , which makes the specifications standardized and highly universal 【Double Size Extension Design】Universal drill bit extension provides 2 extension lengths of 8.26 cm (about 3-1/4 inches) and 14.61 cm (about 5-3/4 inches) , which is suitable for deep hole processing scenarios (like large vases and containers drilling) , and is compatible with the standard drill bit , which makes it easy to fulfill the need of drilling flat bottom holes, Manufacturer: PATNFR