Copper Roves - 7/16" OD for 12 Gauge Nails (1/2 Kg (1.1 lb))

Roves are used when fastening two pieces of wood - typically boat planking - with copper nails to secure the nail so it can't loosen or back out.
Copper roves are slightly conical washers that are pushed over the pointed end of the nail (concave side facing the plank) and "set" using a Rove Set Tool. Then the nail is clipped to length and peened over to form a copper rivet.

Copper Roves are sized according to the wire gauge of the copper nails they are used with (the higher the number, the thinner the nail) so they have a tight fit on the nail.
Copper nails and roves are normally sold by weight.