Rockwell principle DIN and ASTM E18. Easy operation and 3 sec measurements Large Stand provide big parts measurements Rockwell Model or Rockwell Superficial Model available Rockwell Scales : HRC, HRB, HRA, HB30 and more HR available Superficial Scales : HR15N, 30N,45N, HR15T, 30T, 45T Selectable Stand : NX, TX , CAR and MUR