Metallics JTSFS21SS Screw 8 x 1 FH SD TS 18-8 (Jar 100)

It's a #8 by 1 inch flat head self-drilling screw in 18-8 stainless steel, sold as a jar of 100. The flat head seats flush in a countersunk hole, and the self-drilling point cuts its own hole in sheet metal, so no pilot drilling step.

18-8 is austenitic stainless, which is what you specify when a plain or zinc-plated screw would rust, so it holds up in wet interior areas and general exterior work. It is not the grade for constant salt spray or submersion. The JTSFS21SS is that 18-8 material in a #8 by 1 inch flat head self-drilling form.

No. The self-drilling point on the JTSFS21SS forms its own hole as it drives, which is the whole reason to use a TS-style screw on sheet metal, strut, and light-gauge framing. One pass with a driver, no pre-drill and no separate tap.

Flat head is the one you want when the fastener has to finish flush, into a countersunk hole or under a part that sits on top of it, such as plates, trim, and cover work. A hex washer head stands proud and gives you more bearing surface and more torque, so that's the better pick for clamping sheet metal laps or hanging strut. The JTSFS21SS is the flat head version in #8 by 1 inch.

The JTSFS21SS measures 1 inch overall in a #8 diameter, and because it's a flat head the head sinks into the countersink rather than adding to that length. Figure your material thickness plus enough thread past the back face to engage, and keep in mind the self-drilling point consumes some of the tip. For stacked assemblies thicker than about half an inch, step up to a longer screw in the same #8 family.

100 per jar. The jar format is the one to keep on the truck or on the shelf for small-quantity electrical and MRO work, rather than a bulk box you'd buy for a single large run.

Stainless against galvanized steel or aluminum is a common pairing and generally acceptable in dry and ordinary exposures, but it is the stainless that stays intact while the zinc or aluminum gives up material if the joint stays wet. Where it will be permanently damp, isolate or specify a matched-metal fastener. The 18-8 stainless on the JTSFS21SS is the more noble metal in that pair.