Three-quarter inch drive is plant and heavy-vehicle territory, where a dropped socket is a hazard rather than an inconvenience. This is the complete list of 6 extension bars in the range, with part numbers.
Why safety-lock versions exist
A three-quarter inch socket is a substantial piece of steel, and the assemblies it works on are often overhead or at height — truck wheels, crane fixings, structural bolting. A spring detent that holds a socket adequately on a bench is not an adequate answer when the same socket is above someone. Safety-lock bars add a positive pin that must be released deliberately, so the socket cannot part company with the bar under vibration or its own weight.
Torque at this scale is not a hand tool problem
Fasteners that justify three-quarter inch drive are routinely specified above five hundred newton metres, which is beyond what one person can apply to a bar of any reasonable length. That work belongs to a torque multiplier or a powered wrench, and the extension bar in the stack simply has to survive it. The relevant question when choosing a bar here is not how much leverage it gives — it gives none — but whether every component in the stack is rated for the tool driving it.
All 6 lengths
| Length | Length (in) | Type | Teng part number | EAN |
|---|---|---|---|---|
| 100 mm | 3.94 | Safety lock | M340020S-C | 5020385138926 |
| 100 mm | 3.94 | Standard | M340020-C | 5020385138841 |
| 200 mm | 7.87 | Safety lock | M340021S-C | 5020385138933 |
| 200 mm | 7.87 | Standard | M340021-C | 5020385138858 |
| 400 mm | 15.75 | Safety lock | M340022S-C | 5020385138940 |
| 400 mm | 15.75 | Standard | M340022-C | 5020385138865 |
Where this list comes from
Every row is read from the live Teng Tools USA catalogue on the day this page was generated — product record, part number and size taken from the record itself, never transcribed from a printed catalogue or inferred from a pattern. Lengths and retention type are read from the product record; the inch column is an exact conversion, rounded for display. A size that has been discontinued disappears from this list rather than lingering as a part number you cannot order, which is the failure mode of every static spec sheet.
Getting the assembly straight
At this size the socket, bar and fastener want to be genuinely in line, because an off-axis load that a half-inch assembly absorbs will bend or break a component here — and the components are heavy enough to hurt on the way past. Where the geometry will not allow a straight run, the answer is a shorter bar and a repositioned tool rather than persuading the stack into an angle it does not want to sit at.
Bars and sockets are in sockets and accessories; torque tools are in torque equipment.