BSW Mild Steel Zinc Plated Hex Head Bolts & Nuts Supacheap Bolts Hexagon Head Mild Steel BSW bolts are manufactured to Australian Standard 2451and our bright zinc plated finish offers corrosion protection, suitable for general purpose internal and external bolting applications. Supacheap Bolts currently stock 1/4", 5/16", 3/8" and 1/2" diameter bolts up to 1.1/2" in length for certain diameters. Please note: Our Image is of a generic standard bolt and nut and thread lengths vary slightly per size so check with us before ordering if this dimension is of importance. Typically, thread lengths for our hex bolts will be to the recognised international metric standard. All bolt lengths are measured from under the head.