4ml Screw Neck Autosampler Vial with Micro-Insert. The 4ml screw neck glass vial produced by Aijiren is often used in Autosampler. The 4ml 13mm opening is convenient for automatic injection needle injection. The Cap has a center hole. PTFE and Silicone are compounded on both sides to ensure that one side of PTFE faces the reagent inside Vias