Klein Tools 5/16'' Long Nut Driver 18'' Shank

That is what the long-shank version is built for. The shank measures 18 inches (45.7 cm) and the tool is 21.625 inches (54.9 cm) overall, so you get roughly a foot and a half of reach past the handle for nuts set back inside walls, behind equipment, or at the bottom of a deep enclosure.

Yes. The shaft is hollow, which lets it swallow long bolts and studs instead of bottoming out, so you can keep driving a nut down a protruding thread, for example on stacked circuit boards or long machine bolts. Nut size is 5/16 inch.

Same 5/16 inch, 18 inch long nut driver; the tip is the only difference. S1018M has a nut-holding magnet built into the shank so the nut stays put when you are working one-handed overhead or down a wall. S1018 is the non-magnetic version, which is what you want around loose steel filings or where a magnet is a nuisance.

No. It is not insulated and will not protect against electrical shock, so it must not be treated as a 1000V tool. De-energize the circuit before using it, and wear approved eye protection. If you need to work energized, you need a tool specifically rated and marked as insulated.

The handle uses internal flanges that anchor the shaft and resist twisting, and these are built as heavy-duty long-reach drivers. The shaft is chrome plated to resist corrosion, which matters on a tool that lives in a damp crawlspace or panel. Klein states the drivers meet or exceed applicable ASME/ANSI specifications.

For most sheet metal screws, panel nuts, and HVAC hex-head fasteners in the 5/16 inch range, yes, and it is quicker than assembling a ratchet, extension, and socket in a tight cavity. Difference is the hollow shank will pass over a long protruding stud that a standard socket bottoms out on, and a socket set gives you breaker-bar torque this does not. For heavy breakaway torque, stay with the ratchet.

By handle color. This one has an amber Comfordome handle, and Klein color-codes the handles by size so you can grab the right driver out of a pouch without reading the stamp. It weighs 4 oz (113 g), so a few sizes on the belt is no burden.