A7786 110Pcs M6 to M20 Self-Centered Bonded Oil Seal Washer Assortment Kit ?All of washers will be packed in a sturdy transparent plastic case,can be use for a storage box ?Bonded seal consists of a metal ring and a rubber gasket. Metal ring done antirust processing,rubber ring generally uses oil resistant NBR or fluorine rubber ?Bonded washers are used extensively for sealing under the heads of bolts in high pressure applications where coppers washers would be unsuitable. They are often used in hydraulic and pneumatic connections that are subject to extreme pressures Package included: ?10 x M6 Bonded Oil Seal Washer ?10 x M8 Bonded Oil Seal Washer ?10 x M10 Bonded Oil Seal Washer ?20 x M12 Bonded Oil Seal Washer ?20 x M14 Bonded Oil Seal Washer ?20 x M16 Bonded Oil Seal Washer ?10 x M18 Bonded Oil Seal Washer ?10 x M20 Bonded Oil Seal Washer ?1 x Plastic Box