Aijiren flat bottom gas chromatography vials with closures Specifications. Vial, headspace, certified, crimp, clear, flat bottom, 20 mL, 100/pk. Vial size: 22.75 x 75 mm (20 mm cap) Aijiren headspace vials are constructed from type 33 and type 51 COE borosilicate glass, with low metal content, to protect your sample from destablizing or leaching.