Metallics JSWC76 Washer 1/2 Flat Wshr Cu (Jar 100)

The JSWC76 is a 1/2 inch flat washer, so it is sized for 1/2 inch bolts, ground rod clamps, and threaded rod of that diameter.

It is a copper flat washer, called out as Cu in the Metallics designation. Copper is what you want where the washer sits against copper bonding conductors or copper lugs, since pairing copper hardware with copper conductors avoids the dissimilar metal contact you get with a plain steel or zinc washer.

Each jar holds 100 of the 1/2 inch copper flat washers. The jar is the pack format, so ordering one unit gets you the full hundred, not a single washer.

That is the usual reason to stock one. The JSWC76 is an electrical fastener, a 1/2 inch copper flat washer, used to spread load and keep the bearing surface copper where a bonding jumper or ground conductor is bolted down. If the connection is all steel and nothing copper is in contact, a standard steel or stainless flat washer does the same mechanical job for less.

Plain flat, not a split or toothed lock washer. It gives a flat bearing surface under the nut or bolt head and provides no spring tension, so if the connection needs anti-vibration retention you will want a lock washer or a locking nut in addition.