I need this length of extension to complete a phase of a project. I looked at two different types of bit extenders and bought this type because I had no experience with bit extenders. There are two set screws on this model that are free floating and are tightened and loosened with a hex wrench. When using this tool, I found that these screws are very easy to lose. Each screw is around 4.0mm long and can easily be dropped on the floor where they can hide fairly well. So this expansion consists of four parts to form a complete set; Bit, Allen key and two very small set screws. Too many problems to keep track of when they can be avoided.