This Bulte retaining / anti-loss washer, is a flat washer with a thicker cross section and two retaining lips within the inside diameter, which are retained by the screw thread holding the screw in position. This provides the anti-loss facility espcially useful in pre-assembly of fastener with component.
Ease of pre-assembly. Prevents loss of loose screws befor tightening is required
Ideal where a thicker washer is required with components
Use in applications where loss of loose screws is an issue. (Transportation of untightened sub assemblies for example)