INTOOHss Cobalt Drill Bits Set 21PCS Triangle Shank,Industry Drill bits with Golden Ratio Tip,

Thank you for answering my first question. you said, "we takes the highest grade of the first one", do you mean highest grade of tin?

Where are they manufactured?

How do these do drilling through 1/4 steel?

What kind of titanium coating is on these? titanium nitride (tin), titanium carbonitride (ticn), titanium aluminum nitride (tiain)? thanks