Perkin Elmer septa cap online-Aijiren HPLC Vials Pre-Assembled Magnetic Aluminum Screw Cap with Ultra-Low Bleed PTFE/Silicone (White/Blue) Septa - 1.3 mm thick, 100/pk false As the ultra-low bleed septa in the headspace crimp caps are thinner than the standard septa, it is essential to use a higher necked vial to ensure a tight crimp (N9306883).