Drill Bit Holder...Holder

This is the first design I've 3D printed and also my first Thingiverse upload. I wanted to make something simple and easily designed, but useful. I have a lot of drill bits which come in these rubbery holders to secure them. I now have 5 of these holders and am waiting on a 6th in the mail, so I thought I'd make an organizer so I could easily put them on my worktable and see them all easily. This is what I came up with.

It seems to me these rubber bit holders don't vary a lot in their d