[DOUBLE LOCK] The drill bit extension has a locking device at the interface, which, together with the slight magnetism at the bottom of the hole, ensures that the screwdriver bit or drill bit is securely fastened in place and reduces the likelihood of the screwdriver bit or drill bit wobbling and falling out. the locking device on the magnetic bit holder when in use to change bits quickly and easily, greatly improving work efficiency. [PREMIUM QUALITY MATERIAL] The bit holder for impact driver is made of high-quality Material for greater hardness and . This drill extension bit holder is perfect for your impact driver or drill bit set. [UNIVERSAL USE FOR 1/4 INCH] The quick release bit holder works with most 1/4 inch or hex bits, the impact bit holder itself has a 1/4 inch hex shank. This drill extension is a must have in your toolbox. [WIDE USE] The impact extension is suitable for electric screwdrivers, pneumatic screwdrivers, hand screwdrivers, t-handle 1/4 inch screwdrivers, corded drills, cordless drills, pneumatic drills, impact drills, or any other device with a 1/4 inch hex shank. The drill bit extender is perfect for maintenance repairs or diy work in automotive, hardware, home and other fields. [PACKAGE CONTENT] Includes 4 locking bit holders in 4 lengths, 2 inches (60 mm), 4 inches (100 mm), 6 inches (150 mm) and 12 inches (295 mm). Whether it's a project or a complex professional job, this magnetic drill bit holder you have the perfect tool for any situation. Colour:Black & Red Material:Metal Package Contents: 4 * Drill Bit Extension Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.