This is the OEM replacement sensing element for REED's C-380 refrigerant leak detector, designed to restore detection sensitivity once the original sensor wears out from normal use. It plugs directly into the C-380's probe assembly and is calibrated for R-134A and related CFC/HCFC/HFC refrigerant gases. Swapping in a fresh sensor is the standard way to keep the detector's leak-sensing accuracy within factory spec.