The trapezoidal calibrated threaded bars are designed for applications that require precision along the axis. They are used in the the Z-axis of 3D printers or small CNC machines, since they prevent the backlash in the axis direction.
The first digit of the code refers to the bar diameter, and the second digit refers to the pitch. This way, a complete turn of the bar moves the nut the number of millimeters indicated in the second digit.
These bars require at least one trapezoidal nut, as indicated in the table.