Metallics JBWSS38 Washers 3/8 Belleville SS (Jar 100)

It is a spring washer, not a flat spacer. The JBWSS38 is a conical washer built for load bearing tension type applications: you torque it down and the cone flattens, holding a preload on the joint so the connection stays tight as the metal heats, cools, and creeps. That is why they show up under bolted bus, lug, and grounding connections rather than plain flat washers.

One hundred washers, packed in a jar rather than a bag or box, which is what most crews want on a truck or in a parts bin. Total shipping weight for the jar is 0.48 lbs.

They do different jobs. A flat washer only spreads load and a split ring bites the surface, while the JBWSS38 conical washer stores spring tension in the cone and keeps the joint loaded, which is what a load bearing tension application calls for. Where a spec or a connector's instructions calls for a Belleville, substituting a flat washer loses that preload. Where a spec calls for a flat washer under the nut, the Belleville is often used with it, not instead of it.

The jar measures 3 x 3 x 2.15 inches, so it drops into most medium drawer bins and van shelving without decanting. If you keep loose hardware in compartment trays, note that the 100 count is supplied in the jar, not loose.