Slotted bit sockets drive a flat-blade screw from a ratchet, which is the only way to keep a flat blade in the slot while applying real torque. This is the complete list of 3 sizes in 1/4 inch drive.
The slotted head is the worst drive still in service
Every other recess is designed to capture the driver. A slot does the opposite: nothing holds the blade in place except the pressure you apply, and any misalignment lets the blade slide out sideways across the workpiece. It survives because it is the only recess that can be cut with a hacksaw, cleaned out with a fingernail, and driven by a coin in an emergency. On terminal blocks, older machine screws and electrical hardware it is still everywhere.
Blade width is the size that matters
These sockets are sized by the width of the blade, and the correct one is the widest that fits the slot without overhanging the head. A narrow blade concentrates all the load in the middle of the slot and rolls the edges over; an overhanging blade digs into whatever the screw is holding down as soon as it tilts. Blade thickness matters too — it should fill the slot rather than rattle in it — which is why a set covers several widths rather than one blade for everything.
All 3 sizes
| Blade width | Teng part number | EAN |
|---|---|---|
| 4 mm | M141404-C | 5020385131873 |
| 5.5 mm | M1414055-C | 5020385131897 |
| 7 mm | M141407-C | 5020385131880 |
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 blade width in millimetres, as recorded on the product. 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 blade in the slot
A bit socket on a ratchet, held square with the free hand, is the most reliable way to drive a stubborn slotted screw, because the axial force and the torque come from different limbs. Where the screw is genuinely seized, a hand impact driver does it better still: it converts a hammer blow into rotation while simultaneously forcing the blade into the slot, so there is no moment at which the blade can climb out. That combination shifts slotted screws that no amount of steady pressure will move.
Bit sockets are in sockets and accessories; blades and handles are in screwdrivers.