6.8mm to make it much easier to insert/remove bits. would only suggest using this if you mount it upright and let gravity do its thing as the bits will fall out easily otherwise.

also needed some extra spaces (32) to match the number of bits in the gift set i received :)

freecad file included.

printed with PLA and no supports, i did 15% infill and am happy with the result.

update: i had the base plate referenced in a weird way in freecad that was making some geometry duplicated. i'm a freecad newbie so it's best effort only :)