Thread Size: 1/4"-20; Thread Pitch: 20 TPI; Thread Type: Coarse Thread; | Package include: 25 PCS; Hex Drive Size: 7/16" | Material: 304 stainless steel (A2-70) and no exterior finish, greater strength and corrision resistance performance than regular stianless steel or zinc plated fasteners. | Thread Length: 1.5 inch; Head Height: 0.15 inch; | Hex bolts generally require flat & lock washers to evenly distribute the pressure from the head and the nut. You could find the matched hex nut and flat & lock washers in our store with a reasonable price to save your time and money.