Metallics TP338SFC Screws 10-32 x 1-1/4 FH Span TR MS US (100 pcs)

They are 10-32 x 1-1/4 inch machine screws, so the thread is a 10-32 UNF machine screw thread and the overall length under the head is 1-1/4 inches. Because it's a machine screw thread and not a self-tapping point, the hole has to be tapped 10-32 or you need a 10-32 nut on the back side.

These take a spanner (snake-eye) bit, not a Phillips or a hex key. The head has two round holes set either side of center, so you need the matching spanner driver bit in the right size. No standard screwdriver will turn them, which is the whole point of the tamper resistant head.

Yes, it's a flat head screw, so it seats flush in a countersunk or chamfered hole and leaves no protrusion above the surface. That's what makes it usable on cover plates, panels and trims where a raised head would catch.

They're the common answer where you want to stop casual removal of a plate or panel without going to a keyed lock. The spanner head means anyone without the two-pin bit can't back it out, so restrooms, corridors, schools and transit spaces are typical uses. If you only need corrosion resistance or a clean look and nobody is tampering, a standard Phillips flat head 10-32 machine screw is simpler and cheaper to drive. Note this is a machine screw, so it needs a tapped 10-32 hole or a nut behind it, not just a punched hole.

Each pack is 100 pieces of the TP338SFC, all one size (10-32 x 1-1/4 flat head spanner). That's a maintenance-shop quantity rather than a single piece, so if you're standardizing tamper resistant fasteners across a building it covers a lot of plates from one order.