This 2-in-1 Extension Bit Holders has the extension function of the common power tool extension function and also integrate two usage in one bit holders.For one situation, the bit holders remaining at the short status, the 2-in-1 Extension Bit holders can fit with the square sockets and to loose or fix the nuts. For another situation, the bit holders is at the longer status, the bit holders can hold 25mm, 50mm and even 100mm screwdriver bits.