Holds eight vials while supporting the SPME syringe for consistent fiber immersion depth. Cat. No. 57333-U accommodates 4 mL vials only; Cat. No. 57357-U accommodates 15 mL vials. Order the 15 mL vial puck (Cat. No. 57358-U) as a replacement for the 15 mL unit, or to use 15 mL vials with the 4 mL unit. Not for use with automated/HPLC fiber holders.