Ace Rotary-Evaporator/Freeze-Drying Flask Adapter Head W/ O-ring, model 703023 is manufactured by Ace Glass. A flange with two ground planes opposite each other allows the nylon holder on the adapter head to pass through. When the head is rotated 90 ° in either direction, the head and O-ring in the flask tank will form a vacuum seal. No grease, springs or clamps are required.