Plastic, glass, or silanized glass inserts are placed inside of 2mL crimp, snap, or screw thread vials. The diameter of the insert you choose is dependent on the size of the vial opening. Inserts for 8 mm small ID vials (5 mm ID inserts) Inserts for 9 mm wide ID vials (6 mm ID inserts) Inserts for 11 mm wide ID vials (6 mm ID inserts)