Metric fasteners, resembling inch fasteners in style and use, require careful identification to avoid mix-ups. They’re measured in millimeters, with distinctive head markings, and come in three thread types – ISO Coarse, Fine, and Extra-Fine, commonly used in vehicles. Zinc-plated options offer corrosion resistance, suitable for indoor and industrial settings. The 8.8 class, similar to SAE Grade 5, indicates medium carbon steel fasteners with notable tensile strength, used across construction, automotive, and machinery projects.