When designing custom washers, the part designer/engineer should consider the application of the part and the operating environment in order to understand what kind of custom washers are required and in what volume. When designing washers the inside and outside diameter are the critical shapes to consider. Custom washers can be created from many different materials, including aluminum, neoprene, steel, nylon, nickel, titanium, bronze, and rubber. Custom washers are utilized by almost every industry, from telecommunications to automobiles and hydraulic equipment.

The purpose of a custom washer is to distribute the weight of a threaded fastener to prevent loosening or leakage. Rubber washers isolate pressure and distribute it evenly. Generally, rubber washers are placed underneath nuts, axles, and joints.

There are some differences between rubber washers, shims, and collars. Although they all attach in approximately the same way, they have different purposes. Collars are used as stop features for equipment such as speed measuring devices, whereas shims are used to support, provide a better fit, or level a given surface.

Custom collars, custom shims, and custom washers are required when standard sizes do not fit the application, when a special compound is required to withstand specific heats and pressures, or when required to distribute weight in a certain way.

Custom washers are durable and supportive because of the elastic properties of rubber. Rubber washers allow for the even distribution of weight while absorbing and dissipating it. Some common compounds used to manufacture custom washers include silicone, neoprene, and viton.