China VOA Vial Manufacturers, Suppliers, Company - Factory Product Description. 1.ND24 EPA Screw Neck Vials (Clear/Amber). 2.Available with black or white screw caps with 24mm thread. 3.Available as closed top screw seals or with centre hole. 4.Nature PTFE/nature Silicone septa 22*3mm. 5.Environmental analysis.