Self locking washers made for diabolos with a bearing axle. These washers allow the bearing diabolos to remain always tight. No need to tighten up. Once you put these washers on the diabolo, it will not be possible to remove them. The diabolo cannot be disassembled and the axle cannot be changed anymore. 

• Advantage : Bearing diabolos remain tight.
• Drawback : Cannot be removed to switch or to replace the axle.