Nm

nm stands for metric number, also known as metric numbering.

For sewing thread: this indicates the ratio of length in metres to mass in grams. For example, 40Nm means that 40 metres of thread has a mass of 1 gram, while 100Nm means that 100 metres of thread has a mass of 1 gram. The finer the thread, the higher the numerical value. Used as a specification for sewing threads.
The conversion to the Tex system is as follows: Tex=1000/Nm

For sewing needles: indicates the diameter of the needle in 1/100 mm above the hollow.

• Fine needles: Nm 60, Nm 70
• Medium needles: Nm 80, Nm 90
• Thick needles: Nm 100, Nm 110, Nm 120