This is an open style Zinc-Plated Trailer Lug Nut. Zinc Plating helps prevent corrosion experienced in salty environments. 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 fit most 4 lug, 5 lug, 6 lug, and 8 lug trailers with 1/2 inch diameter studs. This is considered the standard lug nut to be used on trailers. For maximum performance, use White Lithium Grease Spray Lubricant and Protector to coat your Wheel studs.