It features a 0.005-inch PTFE/0.120-inch silicone septa bonded to the cap. Designed for use with Wheaton glass EPA vials. Cap Size: 24-400. Cap Material: Polypropylene (PP)/Glass-Filled. Cap Color: White. Cap Style: Open Top. Septa Material: PTFE/Silicone. Wheaton #: W224600.