White PTFE/white Silicone septa, 20mm crimp-top aluminum cap, 10mm centre hole 20 mm Crimp Top Aluminum Silver Cap with PTFE/Silicone Septa . For sealing sample vials for temperatures up to 210 °C. Low background peaks, very low permeability, not recommended for repetitive injections from the same vial. Includes aluminum caps and star springs.