dudetatobeams/bands are metal covered in plastic. As far as i know the grills are also metal. The rest of the housing is plastic. Not sure if the strip connected to the leather strap is metal. I know on other models like the k612's they are plastic.
dudetatoMostly a high density plastic. Very light weight and yet very strong. I don't think I'd pick them to hammer in nails or anything, if that's what you are looking for.