1/2-13 x 3'' Grade 5 USS Coarse Thread Hex Cap Screws, partially threaded,  are made from medium carbon steel and heat-treated. Externally threaded mechanical device 1/4" diameter or larger, with a trimmed hex head and can withstand a minimum of 120,000 PSI tensile strength.  Tempered Grade 5 fasteners are made of medium carbon steel. These fasteners are then quenched and tempered for the additional strength necessary for most automotive uses and other applications where strength is a moderate concern. The grade marking on the head of a Grade 5 fastener is three equally-spaced lines coming out from the center of the head.  Grade 5 is stronger than Grade 2. Bright Zinc Plated. Box of 25.