5/8" Aluminum screw posts are anodized with a black coating that will not come off with ease. The diameter is 3/16" and the post length is 5/8" closed end. The post length is the maximum binding thickness (inside length.) We recommend that you measure your document to obtain the best fit. They come with a 3/8" long screw with a slot on the end for a regular screw driver. The thread size is #8/32 for both the screw and the post. These black screw posts are ideal for scrapbook binding, paint swatches, carpet swatches, book binding and so many more projects. We recommend that you punch or drill a 1/4" hole in your documents to accept these posts.