Alibaba 18mm thread headspace vials with flat bottom for GC Material: USP Type 1, Class A, 33 Borosilicate Glass Dimensions: 22.5 x 46mm/22.5 x 75mm Application: GC system Neck Diameter: 18mm Qty/Pack: 100pcs/pack Volume: 10-20ml Payment: T/T MOQ: 1 pack