Fit two standard sized sports bottles together or even a single large 1 Litre bottle. 
 
Single large hole size diameter: 97 mm
or
Hole size for standard bottles:
Driver side diameter 76 mm
Passenger side diameter 73 mm
 
Versatile design options include;
Pen holder
12 v plug holder
2 x card or ticket holders
Coin holder
2 x Multi-use holder for various size mints packaging or key fob.
Bring your own idea
 
Specify when purchasing your preferred options.