Assortment- Metric Hex Hd C/S 8.8 1600 pcs. in BB40Sold in sets of 1 A metric bolt is a type of fastener that is used to join two or more objects together. It is commonly used in machinery and equipment. Metric class 8. 8 bolts are also known as structural grade bolts. They are made of quenched and tempered medium carbon steel and can be plated with a variety of materials, most commonly zinc. Class 8. 8 bolts see common use in a wide range of industries. Depending on size, they have a proof load of