This is a Gridfinity drill bit holder which can hold 5 drill bits in a 3x1 (2U height so they can stack) space. The .stl file is set up to hold five bits:

• 4mm wide x 48.5mm long bit
• 5mm wide x 60mm long bit
• 6mm wide x 73.6mm long bit
• 8mm wide x 86.3mm long bit
• 10mm wide x 92.6mm long bit

Includes a small drop at the end of the drill bit so you can push down and lever it out of the space.

This works for one of my sets of drill bits. However, I realise everyone has different bits. So I've fully parameterised this, allowing you to set diameter and length of each drill bit, plus some other options.