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.