Half-inch drive is where the torque lives — suspension, hubs, driveshafts, anything torqued into the hundreds of newton metres. This is the complete list of 5 extension bar lengths in the range, with part numbers.
At these torques the bar stores energy
A half-inch bar under two hundred newton metres is a wound spring. When the fastener releases, that stored energy unwinds instantly and the handle moves further and faster than the hand holding it expects. Anyone who has barked their knuckles on a chassis rail knows the feeling. Two habits contain it: pull the handle rather than push it, and know where your hand will end up before you apply the load rather than discovering it afterwards.
Length, leverage and what actually breaks
An in-line extension bar adds no leverage at all — it does not increase the torque reaching the fastener, it only moves the drive. What it does add is twist and off-axis flex, and on a long bar at high torque the flex is enough to tilt the socket on the hex. That tilt is what rounds a large fastener: not insufficient force, but force applied through a socket that is no longer square. The fix is a shorter bar and a proper breaker bar, not a longer everything.
All 5 lengths
| Length | Length (in) | Teng part number | EAN |
|---|---|---|---|
| 63.5 mm | 2.50 | M120020-C | 5020385130524 |
| 125 mm | 4.92 | M120021-C | 5020385130531 |
| 150 mm | 5.91 | M120023-C | 5020385130555 |
| 255 mm | 10.04 | M120022-C | 5020385130548 |
| 500 mm | 19.69 | M120024-C | 5020385132146 |
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 are taken from the product record; the inch column is an exact conversion at 25.4 mm to the inch, 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.
Chrome bars and impact wrenches
A chrome extension bar on an impact wrench is a broken bar waiting to happen. Chrome tools are hardened for wear resistance and a clean fit, and that hardness makes them brittle under repeated hammer blows; impact bars are deliberately softer so they twist rather than shatter. When a chrome bar does fail on a rattle gun it does so instantly and throws fragments, which is a different order of problem from a socket that has simply gone loose.
Chrome bars are in sockets and accessories; impact-rated bars are in impact sockets.