Precision Bit Sizes by Device Class

A Phillips callout is a recess number, not a measurement of your screw. The driver sizes step in a fixed sequence, and the tip figures below are the nominal blade widths that packaging prints against each step. A Torx callout is closer to a dimension: the number tracks the point-to-point distance across the lobes, so T6 really is larger than T5 in a predictable way.

Metric sizes on pentalobe and tri-point drivers are given in millimeters across the feature, and manufacturers do not always agree on the letter code. This is why a pentalobe driver is often sold as both P2 and 0.8 mm. When a listing gives both, trust the millimeter figure.

None of these figures are gauged. They are the callout, which is what you use to buy the right thing, and they will not tell you whether a specific budget bit was actually made to size.

Outer case screws on many phones are pentalobe, typically the 0.8 mm size, sitting either side of the charge port. Inside, brackets and shields move to Phillips at PH000 and PH00, tri-point at Y000, and small Torx at T3 and T5.

The classic error is a T5 in a pentalobe screw. A T5 measures 1.42 mm point to point and a pentalobe 0.8 mm recess is shallow with rounded lobes, so the Torx does engage. It turns roughly a quarter turn and then polishes the lobes away.

The second error is PH00 where the screw wanted PH000. The gap is 0.3 mm of tip width, which is invisible by eye and decisive under load.

Bottom covers on most Windows laptops take PH0. Drive caddies and small internal brackets step down to PH00, and hinge and chassis screws step up to PH1. Slim aluminum machines use pentalobe at the 1.2 mm size on the bottom case, which is a different size from the phone pentalobe and will not do the same job.

Torx turns up on fan and heatsink hardware at T5, T6 and T8. A T5 in a T6 recess turns and then wears the lobes; a T6 will not enter a T5 recess at all, which is the safer of the two mistakes.

On Japanese-built machines a JIS number 0 driver seats deeper than a PH0 in the same screw, and is the better tool if you have one.

Console shells and controller housings are mostly security Torx: T8H on controllers and covers, T9H on outer shells, T10H on drive and chassis hardware. The bit has to be hollow, because a pin stands in the middle of the recess and blocks a solid Torx entirely.

Handheld shells and battery covers use tri-wing, usually TW1 at about 2 mm across the wings. A tri-point Y bit is symmetric and will not drive it, however similar the two look in a photograph.

Retro cartridge and console cases use gamebit, a hollow tube with a square cut through it, in 3.8 mm and 4.5 mm. The two are not interchangeable: the larger will not enter the smaller socket, and the smaller shears the post inside the larger one.

Almost every eyeglass hinge screw is slotted, in blade widths of 1.4 mm, 1.6 mm and 2.0 mm. Sizing here is about blade width relative to the slot, not about torque, because the screws are tiny and the frame is soft.

A blade wider than the slot overhangs at both ends and skates off across the lens the moment it slips. A blade much thinner than the slot twists inside it and widens the slot instead of turning the screw. Fit the blade to the slot length, then check that the blade thickness fills the slot depth.

Sport frames sometimes use PH000 instead. Driving a PH000 recess with a slotted blade splits the cross and ends the screw.

Every recurring precision failure on this list is one step of the callout sequence, not two. PH0 in a PH00 screw. T5 in a T6 recess. A 1.2 mm pentalobe driver against a 0.8 mm screw. Two steps out and the bit simply refuses to enter, which is annoying and harmless. One step out and it enters, grips, and destroys.

The defense is mechanical rather than visual. Set the bit in the recess with no downward force and try to rock it. A correct bit has almost no play. One size down rocks in two directions and you can feel it.

When a set gives you both PH00 and PH000 and you cannot tell them apart in the tray, check them against a screw you have already removed rather than against the label, which rubs off.