a) Made of polystyrene (PS), a transparent, non-toxic, medical-grade substance b) Screw type and pull-off type. Features:a) Made of polystyrene (PS), a transparent, non-toxic, medical-grade substanceb) Screw type and pull-off type are availablec) Supplied in individual, sterile and peel-able polybag or blister packc) Sterile (sterilized by ethylene oxide gas)