These bottletop dispensers are so easy to use! Simply rotate the handpiece and receiver to choose volume desired; raise the handpiece fully and depress to dispense. The low-volume models include a cover to protect the glass column. All models feature a sturdy delivery jet made of PTFE/ETFE. Dispensers fit bottles with 33-mm threaded screw tops and include adapters for 28-, 38-, and 45-mm bottles. Order bottles separately.