External hex, 5/8" x 2-1/2", Zinc plated grade 8

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  Hex bolts

  Bolts with hexagonal heads and machine threads for use with a nut or in a tapped hole. Also known as hex cap screws or machine bolts.

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  Flange bolts

  Flange bolts have a flange on the bottom of the head that distributes the load like a washer.