[TennesseeSquire]

There are four primary considerations for spare bolts and nuts: (1) diameter, (2) pitch, (3) class (strength rating), and length (bolts only). Toyota was nice and standardized on only one pitch for each thread diameter, as follows:

6 mm diameter - 1 mm pitch (iso course) - requires 10 mm wrench to fit head / nut
8 mm diameter - 1.25 mm pitch (iso course) - requires 12 mm wrench to fit head / nut
10 mm diameter - 1.25 mm pitch (iso fine) - requires 14 mm wrench to fit head / nut
12 mm diameter - 1.25 mm pitch (iso other) - requires 17 mm wrench to fit head / nut
14 mm diameter - 1.5 mm pitch (iso fine) - requires 19 mm wrench to fit head / nut
16 mm diameter - 1.5 mm pitch (iso fine) - requires 22 mm wrench to fit head / nut

The class (strength ratings) range from 4T to 11T (Toyota's rating system). However, the simplest way around this is to carrying only SAE Grade 8 (sometimes stamped 10.9) spares. This is the typically the highest strength for a non-stainless bolt or nut and eliminates the risk of not having the strength of bolt/nut required when replacing with a spare. If possible look for a nearby bolt in the same service, note its class stamp, and torque according to the companion bolt (not the torque for the highest class). Ideally went you get home, replace the bolt/nut with the correct class.

Another thing to think about is Toyota uses both hexagon head bolts and hexagon flange bolts that have different torque specfications. I would only carry spare hexagon head bolts and flat washers (to simulate a flange bolt in a pinch).

So now we come to bolt length. Toyota uses bolts of various lengths (same diameter / pitch) depending on the application. I carry 6 mm bolts about 3/4 inch long, 8 mm bolts about 1 inch long, 10 mm bolts about 1-1/4 inch long, 12 mm bolts about 1-1/2 inch long. There are 6 each nuts, washers and bolts of the above size in my traveling tool box, except for the 12 mm size which I only have 4 each.

I don't carry 14 mm and 16 mm bolts, but do carry 2 nuts and washers of each size.

The above may or may not help.

But it sure is nice to know, thanks KLD