5/16" x 1-1/4", US, Zinc plated steel

US Fasteners, 5/16" x 1-1/4", Zinc plated steel
Sheet metal screws Screws with large threads for use in sheet metal sometimes also used in plastic, fiberglass or wood.	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 have a flange on the bottom of the head that distributes the load like a washer.	Machine screws Screws with machine threads for use with a nut or in a tapped hole.
Carriage bolts & Plow bolts Bolts with no drive and machine threads for use with a nut.	Lag bolts Large wood screws technically called lag screws.
Elevator bolts Bolts with a very large flat head and machine threads for use with a nut.	Thumb screws Provides a grip for where hand loosening or tightening is needed. Commonly used in applications such as access panels and where frequent adjustment is required.