A spanner is a non-rotating sleeve of seamless steel tubing that fits over the axle in most casters. They serve the dual purpose of providing a smooth inner raceway for the wheel bearings and strengthening the caster by permitting the legs to be tightened against it.
We at Caster Technology strive to make sure that you will have the caster that is right for you, that is why we offer a complete line of spanners designed for specific handling applications and conditions.