Zinc plated 1-5/8″ outside diameter square strut washers for 1/2″ bolt size are used to secure strut fittings and channel with nuts. Garvin Industries’ strut washers have a zinc plated finish.
Product Page: https://www.garvinindustries.com/fasteners/washers/square-strut-washers/sw-1-2
Garvin Industries Homepage: https://www.garvinindustries.com