Unlike crimp cap vials, require no tools for closure. Manufactured with superior quality (Type 1, Class A) glass, they are available with a round bottom in sizes with usable volumes of 10mL or 20mL. The 18mm vials feature Magnetic Screw Caps which enable magnetic pick up in autosamplers with that capability. Multiple turn threading maintains a tight seal through extreme heating cycles. Septa are Blue Silicone/ PTFE.