On a quarter-inch drive the extension bar is usually what makes a fastener reachable at all, because the ratchet head is small but the spaces are smaller. This is the complete list of 6 lengths, with part numbers.
Pick the shortest bar that reaches
Every millimetre of extension adds twist between your hand and the fastener, and adds distance over which the socket can wander off line. On a small drive the bar is slender enough that the twist is genuinely perceptible: you turn the ratchet, nothing happens, and then the fastener moves in a jump. That lost feel is what stops you noticing a thread beginning to strip. Reach with the shortest bar that clears the obstruction, not the one already in your hand.
Stacking bars
Two bars joined together are not equivalent to one bar of the same total length. Each square connection has clearance in it, and the clearances add up into a noticeable amount of lost motion plus a joint that can flex sideways. Where a long reach is genuinely needed a single long bar is stiffer, more controllable and less likely to shed a socket into the bottom of the engine bay. Keep stacked bars for the case where nothing else physically gets there.
All 6 lengths
| Length | Length (in) | Type | Teng part number | EAN |
|---|---|---|---|---|
| 50 mm | 1.97 | Standard | M140020-C | 5020385130012 |
| 75 mm | 2.95 | Standard | M140023-C | 5020385130777 |
| 100 mm | 3.94 | Standard | M140021-C | 5020385130029 |
| 150 mm | 5.91 | Flexible | M140038-C | 5020385133648 |
| 150 mm | 5.91 | Standard | M140022-C | 5020385130036 |
| 305 mm | 12.01 | Standard | M140024-C | 5020385132214 |
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 as recorded on the product; 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.
Keeping the socket on the bar
A bar working down a blind hole will drop its socket if the retaining detent is worn or the socket is a loose fit, and retrieving a 10 mm socket from inside a subframe is a memorable waste of an afternoon. A wrap of tape across the joint, or a magnet on the drive, costs nothing before you commit to a blind reach. On a flexible bar the risk is higher still because the assembly cannot be kept straight while you withdraw it.
Bars and sockets are in sockets and accessories; ratchets are in ratchets.