Screw Thread Headspace vial – GC Column, HPLC Column, Syringe. Screw Headspace caps, septa, and vials are designed especially for use with Aijiren and CTC rotating or robotic arm samplers. Certified by GC/MS to be contaminate free for VOC analysis. 10ml, 20ml clear or Amber precision thread vial. Magnetic screw caps 8mm center hole.