Supplied in 10-foot sections, Duramax's tough polycarbonate washer strip slides inside the key bore when mounting 100 Series dock bumpers. (100 Series bumpers have an internal channel shaped to accept this washer strip.)
This "washer strip" acts as a continuous washer to accept and distribute the forces of the fastener heads, as well as to prevent the fastener heads from penetrating the rubber bumper during installation.