Headspace crimp vials, the value have 6ml,10ml, 20ml clear and amber to choose, the bottom have flat,rounded and rounded-flat,etc. Match with crimp cap for GC analysis. 20mm Crimp GC Vials 4ml autosampler vial transparent glass vial-made of USP Type I, Class A, 33 borosilicate expanded glass, amber glass vial-made of USP Type 1 Class B 51 borosilicate glass.