hat
Senbòl yo lèt subclassification A, B ak C yo te itilize pou montre pou diferans nan metòd pou fabrikasyon tib la, frèt pwosesis k ap travay, tretman chalè, elatriye.
eng
The subclassification letter symbols A,B and C are used to indicate distinction of method of manufacturing the tube,cold working process,heat treatment,etc.