Tool for standard 6.35mm (1/4inch) hex bits. 

Made so you can use a wrench on the outside if you need more torque.

In metric (13mm outside) for most people, and imperial (1/2inch outside) for the weirdos.

Print a couple of mm's first to check if the bit fits. I had to do mine at +109% in X & Y axis.

Change the Z axis if you want them longer or shorter. 

If you print with 4 walls and 4mm nozzle it will get solid in the part where the bit is.

There are 2 versions; 1 where the inner hex hole goes the whole way through, and 1 version where the inner hex hole is 10mm deep at one end and 15mm at the other end, there are still a small hole you can use to push out the bit if it get stuck.