Metric Class 4.6 Cup Head Bolt & Nut are supplied with a standard Flat Washer. The included washers are supplied at no extra cost. Supacheap Bolts Cup head bolts (also known as Coach or Carriage bolts) are manufactured to Australian Standard AS1390 and have a low profile mushroom head and square under the head which bites into timber preventing turning of the bolt when it is being tightened. Designed for general purpose bolting of timber to timber and timber to steel and the bright zinc plated finish offers corrosion protection, suitable for internal and external bolting applications. Our Hot dipped galvanised finish cup head bolts offer maximum corrosion protection and are suitable for general purpose internal and external bolting and can be use in treated timbers. Supacheap Bolts currently stock M6, M8, M10, M12 and M16 diameter cup head bolts up to 450mm in length for certain diameters. Cup head bolt lengths are measured from under the head.