Shim Washers are very thin washers, designed to be stacked under the head of a screw to create highly precise spacers for a wide range of applications. Shim Washers, or simply 'Shims', are commonly used to ensue that a surface is level, or to remove excess space or play within a mechanism.
Shim Washers are manufactured in highly precise thicknesses of as little as 0.05mm, allowing several washers to be combined in order to calibrate the ideal spacing for an application. These Washers are commonly found within highly precise apparatus with strict spacing requirements, and are generally used specifically for their highly-precise thicknesses.
Due to the demanding manufacture process of creating such precise components, Shim Washers are often not used for general pre-loading and less precision-critical applications - in these applications, alternative Flat Washers are usually recommended.