1. 20ml precision screw headspace vial, 18mm, round bottom, top space vial, strong adsorption. 2. The 20ml precision threaded headspace vial is used for the threaded vial (10ml+20ml) and magnetic screw cap of CTC and TriPlus autosampler. 3. It is convenient to use and does not require any additional tools such as capper and decapper.