Notches are placed on the nozzles side body, by were the number of notches indicates the orifice hole diameter.
Nozzle Orifice Notch Indicator:
1 notch -12 Thou
2 notch -14 Thou
3 notch -16 Thou
4 notch -18 Thou
5 notch -20 Thou
Nozzles are available in the following specifications, detailing orifice diameter mm (inches) and colour code, and engagement length mm (inches) and colour code.