ASTM A194 Grade 8 heavy hex nuts are manufactured from AISI 304 grade stainless steel, and tested to meet ASTM A194 Grade 8. Dimensional specifications are governed by ASME B18.2.2. Grade markings for A194 Grade 8 heavy hex nuts consists of the number 8. Grade 8 stainless steel heavy hex nuts are intended for use in high-pressure and/or high-temperature service with ASTM A193 bolting of similar material, such as B8 and B8 Class 2. Heavy hex nuts provide increased bearing surface area over finished nuts.