Metallics TP221SBC Screws 1/4-20 x 2 Btn Star Pin TR MS 18-8 (100 pcs)

It takes a pin-in-star (pin-in-Torx) bit, not a standard Torx. The TP221SBC head has a six-lobe star recess with a solid pin in the center, so a plain Torx bit will not seat. You need a pin-in-Torx bit of the matching size, and you need it before the screws show up on site, since nothing in a standard bit set will drive them.

Machine screw. The thread runs the full 1/4-20 UNC machine thread form, so it needs a tapped hole or a nut on the back side. It will not cut its own threads in sheet metal. If you only have access to one side and no tapped hole, you want a self-tapping or thread-cutting tamper resistant screw instead, or add a nut, rivnut, or tapped boss to the assembly.

They are 18-8 stainless steel, the austenitic 300-series grade (roughly 18 percent chromium, 8 percent nickel) used for general corrosion resistance. That makes them suitable for exterior and damp interior work such as enclosure covers, grates, and exposed fixture hardware. For salt spray or coastal exposure, 316 stainless is the step up.

It raises the effort, it does not make the joint impossible. A pin-in-star recess defeats common drivers and keyed bits found in a pocket or a hardware store multi-bit, which is why these go into public-area work: restroom accessories, lighting and sign covers, electrical enclosure plates, transit and school fixtures. Anyone with the matching pin-in-Torx bit can still back it out, so treat it as deterrence rather than security hardware.

The button head on the TP221SBC sits on top of the surface with a low domed profile, so it needs no countersink. Drill or punch a straight through hole and the head bears on the face. A flat head tamper screw is the one to use when you need the fastener flush with the surface, and that means a countersunk hole. For thin covers and plates, the button head is usually the simpler install.

100 pieces per pack. That is the sell unit, so one box covers a job with up to 100 fastening points. For institutional standardization work (restroom partitions, fixture guards, meter and panel covers across a building), order by the box and keep the pin-in-star bits in the same count ratio, since those bits wear.