Star Bar Stirring Heads polytetrafluoroethylene set, one of (1210F19), (1210F20), (1210F21), (1210F22) and (1210F23). True paddle configuration in each magnetic polytetrafluoroethylene stirring head. Excellent mixing at slow speeds for biological applications. Features larger vortex for more complete mixing. High strength Alnico-V magnet for maximum coupling. Autoclavable. Available as a kit with all five sizes or individually.