A tempered Alloy Steel. Grade 8 is stronger than grade 5, and is usually used in high strength automobile applications. The finish is unplated.
A plain carbon steel. Grade 5 falls between grade 2 and grade 8 in strength, and is commonly found in automobile applications.
Grade 10.9 bolts are made using quenched and tempered carbon steel, with added amounts of Boron, Manganese and Chromium. Used for bolting large and forged parts, and in automotive metric 10.9 bolts exhibit high tensile strength and good wear resistance.
A quenched and tempered carbon steel. Although class 8.8 is hardened, it is not as strong as class 10.9. It is often used in automobile applications. Class 8.8 is similar to grade 5.