Spacers are put in between the bearings in each wheel. Spacers are used in skates, scooters, waveboards and pretty much anything that rolls with bearings.
You should always use the right kind of spacers with your wheels. If you don't use spacers, the bearings can be excessively stressed, roll badly and end up breaking in a short time. If you use the wrong kind of spacers, the bearings might not be secured properly and they can move from side to side when the wheel is rolling.
The most common spacers are:
6 mm spacers have an "extra ring" in the middle. You can use 6 mm spacers with 6 mm axles.
Always used with 6 mm axles. The spacer is put between the two bearings, and it keeps them securely on the right place, and reduces the inner diameter of the bearings to 6 mm.
How to get the bearings out when using a 6 mm spacer in the wheel
8 mm spacers fit snuggly between the bearings and no "extra ring" is seen from the side. They are used with 8 mm axles
Always used with 8 mm axles. The spacer is put loosely between the bearings, and it centers the wheel bolt when installing the wheels. It reduces the stress directed to the bearings.
How to get the bearings out of a wheel when using a 8 mm spacer
Most spacers are made out of metal, but some can be made out of plastic too. Plastic spacers are not as strong as metal ones, and they split easily. We recommend you to use spacers made out of metal.
In some skates the manufacturer has used mini/micro bearings, and you need to use special spacers for them. Micro bearings have smaller diameter, so standard spacers can't be used. SkatePro does not sell micro bearings or spacers that fit them.
If you have any questions on plastic spacers for bolts. We will give the professional answers to your questions.