1/4" x 3/8", Zinc plated steel

US Fasteners

Hex bolt

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.
Flange bolts

Flange bolts

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

Machine screws

Screws with machine threads for use with a nut or in a tapped hole.