- Screw top vial,2 ml,glass 0.2ml insert. Polypropylene vials are translucent and chemically resistant. They are the vials of choice for pH sensitive samples, sodium or heavy metal analyses. Vial, screw top, polypropylene, with glass insert, 250 µL, 100/pk. Vial size: 12 x 32 mm (12 mm cap) Manufactured from virgin polypropylene