Wheel Pin (12 parts)
A much smaller 'Pin' connector that is used exclusively with small LEGO wheels. (Larger wheels use Technic Pins and Axles.)
The small 'Wheel Pin' connector is extremely similar to the Technic Pin connection, but it is only about 2LU (3.2mm) wide and 3LU (4.8mm) long.
That's 1/3 narrower and 2/5 shorter than a Technic Pin connector.