Description
A Washer 5,5/20x4 is a type of flat washer used with fasteners, where the numbers likely refer to its dimensions in millimeters: an inside diameter (ID) of 5.5 mm, an outside diameter (OD) of 20 mm, and a thickness of 4 mm. This type of washer is designed to sit under the head of a bolt or nut to distribute the load and prevent damage to the surface of the material being fastened.