The system divides the filler metals into eight classes. The class to which a filler metal is assigned is based in most cases on the major element present but in some instances, it has been decided by the similarity ofthe filler metal to others in the same class.

The eight classes are as follows.

1) AL: Filler metals containing aluminium as the major element.
2) AG: Filler metals containing silver as a significant addition, even ifnot the major element.
3) CP: Filler metals containing copper as the major element with an addition ofphosphorus.
4) CU: Filler metals containing copper as the major element, not elsewhere classified.
5) NI: Filler metals containing nickel as the major element.
6) CO: Filler metals containing cobalt as the major element.
7) PD: Filler metals containing palladium, in any amount.
8) AU: Filler metals containing gold, in any amount.

The code for each flller metal consists ofthe two letters for the class followed by three digits, allocated sequentially, starting at 101. Some classes have been sub-divided, with the digits starting at 101 for the first sub-division, 201 forthe second, etc.