Hex bolts have a chamfered point to aid insertion into a tapped hole or nut. Length is measured from under the head. Class 8.8 fasteners are typically made of medium-carbon steel that is quenched and tempered, with 580-600 MPa proof load and 800-830 MPa tensile strength. It is commonly used in the automotive industry and other situations in which strength is a moderate concern. Steels are designated by a 4 number SAE Steel grade. The first two digits indicate the primary materials used to form the steel. The last 2 digits identify the percentage of carbon for the alloy (in hundredths). The steel used in these fasteners has a tensile strength ranging from 100,000 to 150,000 psi (pounds per square inch). Zinc Plating helps to prevent corrosion. Hex head fasteners can be driven with simple wrenches, and require minimal clearance above the fastener because they can be driven or loosened from the side. A threaded fastener"s size name includes information about the major external diameter (in millimeters), followed by the thread pitch (millimeters per thread), which indicates if it is coarse or fine. Coarse threads are better when working with brittle materials; they are sturdier and are easier to thread and unthread compared to fine. Coarse threading also allows for thicker coatings and platings.