We follow ASTM A307 / A563 availbale in various forms and size, products like nuts, bolts,stud bolts and washers etc.Fasteners dimensions, dimensional tolerances are defined in the ASTM A307 standards. ASTM A307 / A563 Hex Bolts standard covers pressure-temperature ratings, materials, dimensions, tolerances,marking, testing, and methods of designating openings for fittings .