Flange bolts feature a broad surface under the head which acts like a washer. Yellow zinc plated fasteners have good corrosion resistant qualities and are a good choice for indoor and industrial applications. Class 8.8 fasteners are heat treated and are similar in strength to grade 5 fasteners. Tensile strength: 800 MPa or about 118,000 p.s.i., similar to SAE grade 5. Head marking 8.8. Made from medium carbon steel.