Jan 26, 2022 · Closure & Septa for 8-425 (8mm) Screw HPLC Vials for Sale Buying aijiren’s 8mm hplc vial requires an 8-425 cap and 8mm septum. aijiren’s Caps are all made of high-quality polypropylene. You can choose whether to have a center hole cap or not. Septa uses a double-sided combination of PTFE and Silicone.