Pololu Wheel 90x10mm Pair
 

These  plastic wheels press-fit onto the 3mm D shafts of our micro metal gearmotors,
mini metal gearmotors, and mini plastic gearmotors with 3mm D-shaft outputs to make a nice drive solution for small robots.
The wheels have silicone tires and measure 90 mm (3.54") in diameter. Six additional mounting holes for 4-40
screws make it possible to use the wheel with our universal mounting hub for 3mm shafts, 4mm shafts, 5mm shafts, and 6mm shafts.
The slots in the six spokes allow additional accessories to be mounted to the wheel (e.g decorations or parts of an encoder system).
The left picture below shows the wheel mounted to a 37D mm metal gearmotor with a universal mounting hub for 6mm shafts.