China PP Closures For HPLC(GC) Sample Vials Manufacturers White 8-425 Open Top PP Cap with 8mm White PTFE/Red Silicone Septa 1.5mm Thick. 100pcs/pk. C0001348. Black 8-425 Open Top Screw Cap with 8mm Red PTFE/White Silicone Septa 1.3mm Thick. 100pcs/pk. C0000132.