these tweezers are made of aisi 420 stainless steel which is basically a steel made for harder stainless steel where we require the steel to be maximum hard then normall stainless steel . the hrc values of this is 50 and you can even use this to hole in any segment with just twisting the surface and can even crush some surfaces to work in with. also this hardened stainless steel is used in micro applications where normally steel fails to serve the required manuals. medical forceps are also made of same stainless steel for micro surgeries