Nuts are 1/4-20" coarse thread which allows quicker removal and built in washer allows for no extra loose fasteners rolling around on the top of the engine.
Nuts are anodized for durability and galling protection and have a lead in chamfer to make starting the nut on the valve cover stud a quicker process. Hex is 7/16" so industry standard valve cover wrenches fit with no issue and there is a little extra height in the nut to make getting to the hex an easier task for the racer for between rounds maintenance.
Nut is .825" overall height with a washer dia. of .560" and are sold individual.