The 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 O-Ring for better sample protection. It is especially made to fit and be used with all Simport Micrewtubes™ Microcentrifuge Tubes. The cap is pierceable with pipet tips as well as with syringe needles.