Harnesses clip in using snap hooks that loop through eyebolts bolted to the car’s chassis. The standard thread for motorsport eyebolts is 7/16″ UNF, which is the thread most roll cage manufacturers and chassis tow points use. Some cars and cages use metric fixings instead.
These are M10 metric eyebolts, part number M30-0027. If your existing chassis points take M10 bolts, or your cage was built to metric specification, these are the correct eyebolts. Fitting UNF eyebolts into metric threads strips the thread, and fitting metric eyebolts into UNF holes is equally damaging. The wrong eyebolt looks like it will go in for the first few turns, which is how most stripped harness anchor threads happen.
One eyebolt per clip-in anchor point. A standard four-point clip-in harness needs two lap eyebolts. If the shoulder straps also clip rather than wrapping around a bar, add two more. A six-point adds the sub strap anchors. Check your harness fitting instructions for the correct torque figure; overtorquing an eyebolt through thin sheet metal without a FISA back plate behind it is the other common fitting error.
If you are not certain which thread your car uses, measure an existing bolt from the same chassis hole. M10 threads run at 1.5mm pitch and the shank measures 10mm across the crests. 7/16″ UNF threads are close but not interchangeable; the M10 bolt will start in a 7/16″ hole and run down two or three turns before binding, which feels like it fits when it does not. Always confirm the thread before ordering eyebolts.






