500mL Double Sidearm Celstir Spinner Flask The Celstir Spinner Flask features an adjustable paddle blade impeller for better mixing. The addition of the bottom dimple to flasks 125 mL and larger improves circulation and reduces the accumulation of cells in the center of the flask. Celstirs provide maximum surface interface between culture and flask atmosphere. Use the Celstirs for microcarrier and suspension cultures such as insect cells, hybridomas, and adapted cell lines. The entire unit may be autoclaved at 121Â