Small nuts on long studs are common in exactly the places a quarter-inch ratchet has to work — clamp bands, sensor brackets, terminal posts. This is the complete list of 11 deep six-point metric sockets in 1/4 inch drive, with part numbers.
The jobs that need a small deep socket
Hose clamp bands with a threaded worm screw, exhaust sensor brackets, battery terminal posts, alternator wiring studs and most panel-mounted terminal blocks put a small nut somewhere down an exposed thread. In every one of those cases a regular socket touches the stud and stops, leaving perhaps two millimetres of engagement on the hex. That is enough to turn the nut when it is loose and nowhere near enough when it is corroded, which is when it matters.
Wall thickness is the constraint
A deep socket in a small size is a thin tube. There is only so much material between the hex form inside and the outside diameter, and on 5 to 8 mm sockets that wall is genuinely slender — which is what lets it drop into a recessed bracket at all. Two consequences follow: do not use one as a drift or a spacer, and do not put a small deep socket on an impact wrench. Both failures split the socket along its length rather than deforming it, and they do it without warning.
All 11 deep sizes
| Size | Decimal inch | Teng part number | EAN |
|---|---|---|---|
| 4 mm | 0.1575 | M140604-C | 5020385132733 |
| 5 mm | 0.1969 | M140605-C | 5020385132092 |
| 5.5 mm | 0.2165 | M1406055-C | 5020385132757 |
| 6 mm | 0.2362 | M140606-C | 5020385130166 |
| 7 mm | 0.2756 | M140607-C | 5020385130173 |
| 8 mm | 0.3150 | M140608-C | 5020385130180 |
| 9 mm | 0.3543 | M140609-C | 5020385132108 |
| 10 mm | 0.3937 | M140610-C | 5020385130197 |
| 11 mm | 0.4331 | M140611-C | 5020385132115 |
| 12 mm | 0.4724 | M140612-C | 5020385130203 |
| 13 mm | 0.5118 | M140613-C | 5020385130210 |
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. Deep and regular sockets in the same size carry different part numbers and are listed separately. 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. Decimal inch equivalents are exact conversions at 25.4 mm to the inch, rounded for display only. They are given for cross-referencing against an imperial drawing, not as a claim that a metric socket fits an imperial fastener — it does not.
Deep socket or nut driver
For a small nut that is merely captive rather than tight, a nut driver often beats a deep socket and ratchet: it spins continuously, it reaches down a stud the same way, and it takes one hand instead of two. The deep socket wins the moment torque matters, because a screwdriver handle cannot deliver much and a ratchet can. Knowing which problem you have before you start saves swapping tools halfway down a bracket.
Sockets are in sockets and accessories; driver handles are in screwdrivers.