... and aeration, anti-skid and secure, wears well, non-sagging,non-dirt, and easy to install 4) Hot galvanizing standard ... steel & Low carbon steel, etc5Surface TreatmentBlack, self colour, hot dip galvanized, painted, spray coating 6Grating StylePlain / Smooth, Serrated /teeth, I bar, serrated ... Australia: AS1657-1985,Germany: DIN24537-1-2006, Japan:JIS steel grating for ceiling grate cover (factory)