round bottom headspace gas chromatography pp caps Alibaba Aijiren 18mm crimp top headspace vials with flat bottom. 2021 - 07 - 06. The Chromatography Direct range of 20mm Crimp Top Headspace Vials and Caps are available in 20ml Amber and Clear, 10ml and 6ml in a variety of flat and round bottom - suitable for CTC, Perkin Elmer and Aijiren autosamplers.