This insert is a blind insert similar to a wall anchor. Available in 2 lengths of each size (6-32, 10-24 and 1/4-20). They are great for placing threads into materials like soft plastics and brittle materials which otherwise could not be threaded. These inserts are plated steel, but are available in brass. Special coatings can be applied to the insert allowing them to be water-resistant, corrosion resistant or to prevent scratching or marring.