This is an open style Zinc-Plated Trailer Lug Nut. Zinc Plating helps prevent corrosion. These lug nuts have a standard trailer 1/2-20 Thread. You use a 13/16 socket/lug wrench for removal and installation. This Trailer Lug Nut will will most 4 lug, 5 lug, 6 lug, and 8 lug trailers with 1/2 inch diameter studs.