The HI76483A/P are spare dissolved oxygen screwcap membranes made especially for Hanna’s HI76483 DO probe. The PTFE membranes separate the probes cathode and anode from the sample being measured. Oxygen diffuses across the membrane and interacts with the polarographic system to produce a current proportional to oxygen concentration. Each cap is easily filled with HI7041 electrolyte and screwed on to the probe.