18mm Screw Top w/ 1.6 mm Red PTFE/Butyl Septa - LCGC Vials • Caps have 8mm opening • Caps with septa pre-inserted • Excellent Performance on all CTC Analytics Systems Requiring Magnet Compatible Closures (i.e. Varian, L.E.A.P., Tekmar, and Perkin Elmer) • Fits screw top headspace vials • Chlorobutyl rubber faced w/ PTFE