Three-eighths drive is the size most work gets done on, and the six-point metric regular socket is the workhorse of that range. This is the complete list of 16 sizes currently in the catalogue, smallest to largest, with the Teng part number for each.
Why 3/8 inch drive is the default
A drive size is a compromise between how much torque the square can carry and how much room the tool needs. Quarter-inch drive runs out of strength somewhere around 25 Nm and half-inch drive is too bulky to reach into a bay full of loom and bracketry. Three-eighths sits between them: strong enough for suspension-adjacent fasteners, slim enough that a socket and ratchet will still turn in a confined space. If a workshop owns one socket set, this is the one it owns.
Six point against twelve point
A six-point socket contacts all six flats of the fastener. A twelve-point contacts the same flats but with half the material behind each contact face, and it engages every thirty degrees rather than every sixty, which is why it feels quicker to locate. The trade is strength at the corners. On a fastener that is tight, corroded or already slightly rounded, six point is the one that survives — the load spreads across the flat rather than concentrating where the metal is thinnest. Twelve point earns its place where swing is restricted and the fastener is not fighting you.
All 16 sizes
| Size | Decimal inch | Teng part number | EAN |
|---|---|---|---|
| 7 mm | 0.2756 | M380507-C | 5020385132801 |
| 8 mm | 0.3150 | M380508-C | 5020385130326 |
| 9 mm | 0.3543 | M380509-C | 5020385130333 |
| 10 mm | 0.3937 | M380510-C | 5020385130340 |
| 11 mm | 0.4331 | M380511-C | 5020385130357 |
| 12 mm | 0.4724 | M380512-C | 5020385130364 |
| 13 mm | 0.5118 | M380513-C | 5020385130371 |
| 14 mm | 0.5512 | M380514-C | 5020385130388 |
| 15 mm | 0.5906 | M380515-C | 5020385130395 |
| 16 mm | 0.6299 | M380516-C | 5020385130401 |
| 17 mm | 0.6693 | M380517-C | 5020385130418 |
| 18 mm | 0.7087 | M380518-C | 5020385130425 |
| 19 mm | 0.7480 | M380519-C | 5020385130432 |
| 20 mm | 0.7874 | M380520-C | 5020385133495 |
| 21 mm | 0.8268 | M380521-C | 5020385130449 |
| 22 mm | 0.8661 | M380522-C | 5020385130456 |
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. Metric sizes are the across-flats dimension in millimetres, exactly as the socket is stamped. 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.
Choosing between two adjacent sizes
If a socket goes on with a perceptible rock, it is the wrong one. The next size down will feel like it does not want to start, and that is the correct feeling — a hex socket should need a light push, not drop on. The rock is the socket bearing on the corners of the fastener instead of the flats, and the corners are what shear away under load. This matters most in the crowded part of the range: 12, 13 and 14 mm sit close enough together that a socket grabbed by eye is regularly one size out.
The rest of the range is in sockets and accessories, and pre-built ranges are in socket sets.