Bi-metal crimp closures support transportation of the vial via magnet, as for e.g. in the CTC Combi PAL, the Shimadzu AOC 5000/6000 or the Gerstel autosampler. They are generally more difficult to crimp/decap which is why Headspace screw neck vials N 18 may be a more convenient alternative. This product has no liner (septa).