SAE sockets are sized by the distance across the flats of the fastener in fractions of an inch. This is the complete list of 10 six-point SAE regular sockets in 3/8 inch drive, ordered smallest to largest with the Teng part number for each.
Reading an SAE size
A socket marked 9/16 measures nine sixteenths of an inch across the flats of the hex it fits — it says nothing about the thread, the bolt diameter or the drive. That last point catches people out constantly: a 1/2 inch socket on 3/8 inch drive is a half-inch fastener turned by a three-eighths square, and the two numbers describe different ends of the same tool. Teng marks these AF, for across flats, which is the unambiguous way to say it.
The metric near-misses that cost fasteners
Imperial and metric sizes interleave without ever quite meeting, and a handful of pairs are close enough to go on and far enough apart to do damage. The worst is 3/8 inch against 10 mm: the socket is roughly nineteen thousandths of an inch undersize, it seats convincingly, and it rounds the head on the first serious pull. Conversely 3/4 inch and 19 mm are within two thousandths and genuinely interchangeable. The millimetre column below is there so those distances are visible rather than guessed.
All 10 SAE sizes
| Size | Decimal inch | Millimetres | Teng part number | EAN |
|---|---|---|---|---|
| 5/16 in | 0.3125 | 7.94 | M380110-C | 5020385132399 |
| 3/8 in | 0.3750 | 9.52 | M380112-C | 5020385132405 |
| 7/16 in | 0.4375 | 11.11 | M380114-C | 5020385132412 |
| 1/2 in | 0.5000 | 12.70 | M380116-C | 5020385132429 |
| 9/16 in | 0.5625 | 14.29 | M380118-C | 5020385132436 |
| 5/8 in | 0.6250 | 15.88 | M380120-C | 5020385132443 |
| 11/16 in | 0.6875 | 17.46 | M380122-C | 5020385132450 |
| 3/4 in | 0.7500 | 19.05 | M380124-C | 5020385132467 |
| 13/16 in | 0.8125 | 20.64 | M380126-C | 5020385132474 |
| 7/8 in | 0.8750 | 22.22 | M380128-C | 5020385132481 |
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. Sizes are as the socket is stamped, in fractions of an inch across the flats. 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. AF means "across flats": the distance between two opposite faces of the hex, which is what the socket actually grips. Millimetre equivalents are exact conversions at 25.4 mm to the inch and are provided for cross-referencing only.
Where SAE fasteners still turn up
Domestic vehicles, older agricultural and construction plant, US-built machine tools and a great deal of plumbing and structural hardware remain imperial, and plenty of assemblies are mixed — a metric engine in an imperial chassis is ordinary rather than unusual. Keeping the two ranges physically separated in the drawer is worth more than any conversion chart, because the error happens at the moment of reaching, not at the moment of thinking.
The full range is in sockets and accessories, and complete ranges in socket sets.