... Sparking Tool hearing needles. 2.Size:300-600mm 3.Hand Tools,safety tools 4.Corrosion resistant 5. ... Surface treatment 1) Electrostatic spraying 2) Natural color 3) Passivation4.Specs 300mm,400mm,500mm,600,700mm,800mm, ... used in medical apparatus and instruments, food industry ect. 3) Weakness: Low strength, low hardness. HRC<10°Terrace ... . Hearing needle,Ball head hearing needle,No spark hearing needle