As faixas de durezas para os TUBOS TREFILADOS conforme a Norma DIN EN 10305-2 são :
BK (C ) : 80/95 HRb
BKW (LC ) : 55/70 HRb
GBK (A ) : 35/55 HRb
NBK (N ) : 40/65 HRb
C ) : 80/95 HRb LC ) : 55/70 HRb A ) : 35/55 HRb N ) : 40/65 HRb