These septa are designed to fit the DURAN® open-top cap product family.Septa are available in a variety of materials and thicknesses. PTFE Natural Rubber are moderately priced seals for GC and HPLC with good chemical properties. They are ideal for multiple injections due to high resealability, but not as easy to penetrate as PTFE/RR. PTFE/High Performance Rubber is a highly pure synthetic red