Gr.5 Serrated Hex Flange Machine Bolts: This bolt features a integrated flange with serrations under the head as well as a fully threaded shank. Available with either zinc and/or trivalent (rohs) finish, sizes range from #6 ~ 5/8" diameters. [A non-indented head is recommended as it prevents grease and dirt from accumulating on the head while providing a higher quality finish and appearance.]