Heavy Hexagon Bolts (or just Hexagon Bolts) is a general term for all bolts with a hexagonal head. The term ‘hexagon bolts’ is often used for bolts with a smooth shoulder, and the term ‘hexagon set screw’ or ‘machine bolt’ is often used for fully-threaded bolts. They are usually delivered standard with a 3.1 certificate and are ‘marked’ with a quality indication and a manufacturer’s logo.
Standard: ANSI B18.2.1
The diameters are specified in inches (f.e. 5/8”). For bolts with a metric diameter (f.e. M16) but an ASTM quality, there are generally somewhat fewer options and those that are available do not fall under the ANSI B18.2.1.
Hexagon bolts can be obtained in many different diameters as well as many different qualities and types.