YSI 5909 [605307] DO Cap Membrane Kit. Used with Polarographic probes. Includes bottle of electrolyte, 1 sanding disc and 6 screw-on cap membranes. 2.00 Mil PE membranes. Blue cap. Response Time (T95 - from 0 to 100%) = 17 seconds. Flow Dependence After 4 Minutes = 18%. Required Flow Rate = 3 inches/second.