Axle rods with 3-mm diameter are usually used for plastic wheels made in Europe and Asia. This includes the MiniScience brand Gear-Wheel, Plastic gears and small front wheels such as those used in Solar Car Kit.
These axles fit snugly in wheels or gears with 3-mm bore and often there is no need to use additional fillers or glue.
Axles with 3-mm diameter are 75 mm long.
Available in packs of 100 and packs of 1000.
Note to manufacturers and producers of technology training kits:
The actual diameter of the hole in European and Asian plastic wheels is 2.9 millimeters so that the axle will fit snugly. So the 3-mm is the nominal diameter of such wheels.
If you are producing your own plastic or wooden wheels, please consider the flexibility of your materials and make the hole smaller as needed in order to avoid any need to glue or fillers.