2021/8/5 · 18mm Screw Neck Closures 18mm screw neck vials with magnetic screw seals for CTC is a new product in the headspace market where the jaws dominate. Especially for magnetic caps that are difficult to crimp, screw caps are a convenient alternative. 18mm Screw Neck Closures with Vial are preferentially used in instruments: CTC PAL, Varian, Gerstel, Atas, Shimadzu, Aijiren.