410 stainless steel is strong, wear resistant, and mildly chemical resistant. These screws have a hex head for a secure grip with a wrench and a flange to reduce the risk of crushing thin metal. They save you time and effort by drilling their own holes and fastening in a single operation. 410 stainless steel screws are magnetic and not for use with aluminum. Length is measured from under the flange. Head height includes the flange.