Dia/Thread Size
The thread size of a nut is typically expressed as the diameter (Dia) followed by the number of threads per inch (TPI). The first part of the size designation, like 1/4", 5/16", etc., represents the diameter of the nut's hole, which corresponds to the diameter of the bolt it's intended for. The number after the diameter, like "-20" in 1/4"-20, indicates the number of threads per inch of the bolt's threaded section.
