This is the hard to find ball bearing busing found on many of the more expensive beauty shears today. This ball bearing 7 MM in diameter with a 4 mm hole. This is the standard size for ball bearing on most shears. This can not be substituted for other types of washers are shears not designed to have ball bearing bushings. The experienced and prepared sharpener will have one of these parts ready in case this piece becomes missing from a shear. Suggested replacement of this highly technical part to a stylist would be $10.00.