1/2" Black screw post extensions are wonderful to use for book binding when you need just a little bit more length. This extension is 3/16" in diameter with a thread size of #8/32 and the length of the post is 1/2". The black anodize color makes it stick out from the aluminum with the way it shines. These black aluminum screwpost extensions are durable so they won't break, and keep your bound document secure.