ASTM A320 Grade L7 studs are manufactured from AISI 4140/4142 alloy steel, quenched and tempered. Dimensional specifications are governed by ASME B18.31.2. Grade markings consists of both the grade symbol "L7" and the manufacturer's identification mark on one end of each stud 3/8? diameter and larger. Manufacturer's marking may be placed on other end if insufficient space. A320 L7 all thread studs having diameters above 1? are most common in 8UN (8 threads per inch) thread pitch. A320 L7 stud bolts are intended for low temperature service. They have the same chemical and physical properties as ASTM A193 Grade B7, but must meet a Charpy impact value of 20 lb-ft at -150F to ensure satisfactory performance in low temperature services. These fasteners are commonly used for valves, flanges, fittings, and pressure vessels.