Features:
Use in a pair of 2 pieces so that the spherical convex and concave surfaces are interchanged. Even if the shaft of the bolt is misaligned, it will fit snugly into the seat of the other, bolt and nut to ensure a tight fit. High carbon steel is heat treated for extra strength. See JIS B 5213 for standard.
[Use]
Use as an adjustment washer when the seat of the others part and bolt is not completely adhered.