YSI #5775 stretch membrane kit, 1.0 mil PTFE, with 30 regular membranes and one bottle of fill solution for 55 meters or 5719, 5739, 5750, and Rapid Pulse probes
Membrane kit, 1.0 mil PTFE, with black threaded caps and one bottle of fill solution for YSI meters 5905, 5010, 5239, 550, 556, 85, MPS, and Pro Plus with a polarographic sensor
Membrane kit, 1.25 mil PE, with yellow threaded caps and one bottle of fill solution for meters 200A, 550A, DO-200, and 556 with older software and with a polarographic sensor or Pro Series polarographic sensors.
Membrane kit, 2.0 mil PE, with blue threaded caps and one bottle of fill solution for 556 meter with 1.03 software and with a polarographic sensor or Pro Series polarographic sensors.