The T504AQX screw cap incorporates a pierceable septum made of chemically resistant PTFE on the outside and silicone on the inside, both components being stable over a broad range of temperatures. The septum also acts as a silicone washer seal for better sample protection. It is especially made to fit and be used with all Simport® Sample Tubes with external threads. The cap is pierceable with pipet tips as well as with syringe needles.