New products: 40×7 mm wheels

We now have 40mm-diameter wheels (available in black, red, and white) in the same thin style as our 32×7 mm wheels, which help fill the void between those and the 60×8 mm wheels that were previously our next size up. Black Pololu wheels with 90, 80, 70, 60, 40, and 32 mm diameters...