Metallics JSS858 Screw 8-32 x 5/8 SKT S-Scr Cup St-Bl (Jar 100)

It's a cup point. The end is hollowed into a ring-shaped edge that bites slightly into the mating surface, which gives a strong grip on a shaft, rod, or bus but leaves a mark. If you need to clamp something you will later need to remove and reposition without scarring, a flat or nylon-tip set screw is the better choice; cup point is the standard for a permanent set.

It's a socket set screw, so it drives with a hex key (Allen wrench) in the internal socket, not a screwdriver. There's no head above the surface, which is why these are used where the fastener has to sit flush or fully inside a tapped boss.

Each jar holds 100 of the 8-32 x 5/8 inch screws, and the jar is the pack type, so you buy them by the jar rather than individually. That quantity suits an electrician or MRO stockroom keeping a common set screw size on the truck or shelf.

Steel with a black finish. Plain black-finish steel is for dry interior use; it has no corrosion-resistant plating, so for wet, damp, or exterior work you want a stainless or zinc-plated set screw in the same 8-32 x 5/8 size instead.