13mm Septa found in: 13mm Septa For Screw Thread Vials, SEPTA 13MM DIA 100/PK, Blk S/Cap w/Red PTFE/Sil,13mm with Septa, Silicone Septa for Waste Wash.. PTFE Disk septa are inert chemically inert PFTE Red Rubber septa are economical for many GC applications PTFE/Silicone septa are most popular for HPLC and IC applications Pre-slit septa are easier to pierce with thin gauge needles