Septa for 8-425 Screw Thread Caps are constructed of PTFE, PTFE/rubber, or PTFE/silicone to suit a variety of applications. Shop Thermo Scientific™ 8mm Autosampler Thermo Scientific™ 8mm Autosampler Vial Septa Seal, 8mm; Red PTFE/white silicone; 100/pk. Thermo Scientific™ 8mm Autosampler Vial Septa | Fisher Scientific