Description. SDS. Pricing. 27020. black polypropylene hole cap, thread for 18-400, PTFE/silicone, septum thickness 1.5 mm, for use with 15 mL vial, pkg of 100 ea. Expand. Hide. 27018. black polypropylene hole cap, thread for 13-425, PTFE/silicone, septum thickness 1.5 mm, for use with 4 mL vial, pkg of 100 ea.