Torx bit sockets put a Torx driver on the end of a ratchet, which is the only practical way to apply real torque to a Torx screw. This is the complete list of 7 sizes in 1/4 inch drive, with the Teng part number for each.
What the Torx form actually does
A Torx recess is a six-lobed star with rounded lobes, and the faces it drives against are close to perpendicular to the direction of rotation. A Phillips recess, by contrast, is a tapered cross whose faces are angled, so torque generates a force pushing the driver back out of the screw. Torx generates almost none of that, which is why a Torx fastener can be driven to full torque without the downward pressure a cross-head demands, and why it survives being undone and done up many more times.
The size number is a code, not a measurement
A T20 is not twenty of anything. The numbers are an index into a table of standard geometries, and the steps between them are not uniform — the gap between T10 and T15 is not the same as the gap between T40 and T45. That has a practical consequence: you cannot interpolate. If a screw is not T25 and not T30, there is no size between them, and the answer is that you have misread the recess or it is a different standard altogether.
All 7 sizes
| Torx size | Teng part number | EAN |
|---|---|---|
| T10 | M141210T-C | 5020385133877 |
| T15 | M141215T-C | 5020385133891 |
| T20 | M141220T-C | 5020385133914 |
| T25 | M141225T-C | 5020385133938 |
| T27 | M141227T-C | 5020385133952 |
| T30 | M141230T-C | 5020385133976 |
| T40 | M141240T-C | 5020385133990 |
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 use the ISO 10664 T designation; Teng marks its Torx tools with a TX prefix and the number is identical. 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.
Torx, tamper-proof Torx and external Torx
Three things share the name and none of them interchange. Standard Torx is the plain six-lobed recess listed here. Tamper-proof Torx has a pin in the centre of the recess and needs a driver bored to clear it — a standard bit will not enter at all. External Torx, marked with an E and a number, is the inverse: a male star head that a socket fits over. An E10 socket and a T10 bit are entirely different tools and the numbers do not correspond.
Bit sockets are in sockets and accessories; keys and drivers are in hex and TX keys.