What size is that little tiny nut you're trying to replace? What about that little screw... how can you tell a #3-56 from an M3 without a micrometer or a trip to the hardware store?
Thread Detective® to the rescue!
The Mini Thread Detective has a total of 21 special steel fittings, each with a different SAE (inch) or metric (mm) screw size. Each size has both male and female threads so you can identify machine screws and nuts. The SAE sizes are all strung together on a wire lanyard, and the metric sizes are all strung together on a second lanyard. Both lanyards are connected to a small metal tag with an 85mm (3 3/8") ruler with both metric and SAE markings. The fittings are separated by shatterproof, color-coded plastic dividers (blue for metric, red for SAE). Each fitting has its thread size permanently printed in bold numbers. Loops at both ends of each lanyard let you hang them near your workbench or in the trailer. The extra-long lanyards let you reach into tight places when removing the mystery hardware isn't practical.
This Standard kit covers very small thread sizes used on miniature machine screws.
SAE (inch) sizes: 1-64, 1-72, 2-56, 2-64, 3-48, 3-56, 4-40, 4-48, 5-40*
Metric (mm) sizes: M1.2x0.25, M1.6x0.2, M1.6x0.35, M1.8x0.35, M2.5x0.35, M2.5x0.4, M2x0.25, M2x0.4, M3.5x0.35, M3.5x0.6, M3x0.35, M3x0.5
*Note: SAE machine screw sizes #1 through #5 measure 0.07" through 0.12" diameter. These are extremely small screws used mostly in computers and other miniature assemblies. You are unlikely to find sizes this small on a racecar.