Vials for HPLC | Sigma-Aldrich. 27273. black polypropylene hole cap, 10-425 thread, PTFE/silicone, septum thickness 1.5 mm, for use with 2 mL vial (large opening), pkg of 100 ea. Supelco. pricing. SDS. 27018. black polypropylene hole cap, 13-425 thread, PTFE/silicone, septum thickness 1.5 mm, for use with 4 mL vial, pkg of 100 ea. Supelco.