2-1/2", 9

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.
Socket product

Socket screws

Screws with an allen wrench drive.
Set screw

Set screws

Screws with no head and machine threads for use in a tapped hole.
Nut

Nuts

Nuts have internal machine threads, for use with machine thread bolts and screws.
Shoulder bolt

Shoulder bolts

Screws with an unthreaded shoulder that is larger in diameter than the threads. Also known as stripper bolts.