Metallics CSF6F Anchors 3/16 x 4 Flat Hd Phil CS Blue St-zn (Jar 100)

Concrete screws of this type cut their own thread in solid concrete, brick, and the solid webs of block. In hollow block, the screw has to land in a web, not a void, and the 4 inch length makes it easy to drill straight through a face shell into air. Lay out on the webs or switch to a toggle or sleeve anchor sized for hollow wall. Drywall and plaster alone will not hold it.

100 pieces per jar. The jar is the pack type, so you are buying a sealed container of 100 rather than a loose count, which is the usual way electricians stock a single length for repeat strut and box mounting.

They are blue climaseal-type zinc coated carbon steel, which is a corrosion-resistant coating suited to interior work and intermittent damp exposure. For permanently wet, exterior-submerged, or chemically aggressive conditions, use a stainless anchor instead.

Flat head is the countersinking option: it pulls down into a countersunk or thin fixture hole and sits flush or near flush, which is what you want under conduit straps, backer plates, and anything a cover rides over. If you are mounting strut or a clamp where you can drive with an impact and want more torque capacity and a washer face bearing on the surface, a hex washer head version is the better pick.

The 4 inch length is for getting through thick standoff before the embedment starts, for example mounting through furring, a sleeper, rigid insulation, or a thick plate into the concrete behind. Embedment is length minus the thickness of whatever you are fastening through, so if you only have a thin strap against bare concrete a shorter screw gives the same hold with less drilling.

Order Metallics CSF6F. That designation covers the 3/16 by 4 inch flat head Phillips carbon steel blue zinc screw supplied 100 to a jar.