Blue 9-425 Open Top Ribbed Screw Cap with 9mm Septa Polyimide/Silicone 1mm Thick suitable for PFAS testing Part No. CP-B-04-11-04PE Unit/Measure: PK/1000 Request a Sample Suitable for PFAS testing. When you cannot use PTFE as a liner - this polyimide/silicone-lined closure is the perfect alternative.