Metallics JSSMSS63 Screw M6 x 6 SKT S-Scr Cup 18-8 (Jar 100)

It's an M6 x 6 mm socket set screw with a cup point, made from 18-8 stainless steel. Set screws like this have no head, so they seat flush or below the surface and the cup point bites into a shaft or bar to lock a collar, knob, or fitting in place. Metallics part number JSSMSS63.

No. M6 is a metric thread at 1 mm pitch and will not engage a 1/4-20 UNC hole, even though the diameters are close. If the equipment is imperial, order an imperial set screw. Metric M6 threaded components are what this one fits.

100 pieces per jar. The pack type is a jar rather than a bag or box, which is what you want in a van or on a service cart where loose fasteners get lost.

It's a socket drive, so you need a hex (Allen) key, not a screwdriver. Standard M6 socket set screws take a 3 mm hex key. Check the socket with the key before you torque it, since an undersized key will round the socket out.

18-8 is the common austenitic stainless grade (the 302/304 family) and it handles general outdoor and damp indoor exposure well. It is not the choice for direct salt spray or coastal marine service, where a 316 stainless fastener is the better call. For typical electrical enclosures, fixture mounting, and equipment set screws, 18-8 is the standard spec.

Cup point, which is what the JSSMSS63 is. The cup digs a small crater into the shaft and resists rotation better than a flat point, so it's the usual choice for permanent or semi-permanent collar, pulley, and knob mounting. Use a flat point instead when you need to reposition the part repeatedly and don't want the shaft marred.

The 6 mm figure is the screw's overall length, and on a headless set screw that is the full body length, so it gives you roughly one diameter of thread engagement in an M6 tapped hole. On a thin collar it can sit flush or just below the surface; if your boss is thicker than 6 mm the screw will bottom out below flush and you may want a longer M6 set screw to reach the shaft.