Cap, Crimp, Open Top Gold Magnetic, 20mm (10mm hole) with 20mm Natural PTFE/White Silicone Septa 3mm Thick. 100pcs/pk. 41311012, Vial, Screw Top Headspace, 20mL Headspace Vial Caps at Thomas Scientific. This magnetic screw cap has been developed for the CTC instrument. The vial has a precision thread with numberous threads to force the septa