The air in the subterranean vault of the Royal Metrology Institute was kept at a constant twenty degrees Celsius, plus or minus zero-point-one degrees. To Master Inspector Elias Thorne, it smelled not of dust, but of precision—ozone, light machine oil, and the cold, sharp scent of steel.

| Tolerance class | Linear (mm) | Angular (degrees/min) | |---|---|---| | f (fine) | ±0.05 | ±0°30' | | m (medium) | ±0.1 | ±1° | | c (coarse) | ±0.2 | ±1°30' |

The specific needed for a press fit or sliding fit?