The 780417A is a replacement membrane pack containing 10 membranes designed for use with EXTECH dissolved oxygen probes, including those used in the SDL150 and 407510 dissolved oxygen meters. These membranes are essential consumable components for the polarographic-type oxygen probe, which measures dissolved oxygen concentration from 0 to 20.0 mg/L and oxygen saturation from 0 to 100.0%. The membranes work in conjunction with the probe's internal electrolyte and diaphragm assembly to enable accurate oxygen measurements across a temperature range of 0 to 50°C (32 to 122°F). Replacement membranes are required periodically to maintain measurement accuracy and probe performance in water quality monitoring, aquaculture, wastewater treatment, and laboratory applications.