This stand is designed for an electric MiniWare ES15 screw driver. 

• the inner hole is long enough to hold the ES15 with an extra bit inserted
• the outer rings take 30 bits in total (4mm type)
• the fit for the bits isn't too tight so they're easy to access.

The stand is designed to stay on the workbench and provide easy & quick access to everything - that's why i went with a rather loose fit for the bits.