FLOAT SWICTH "Water over flow safety device", single or set, addition or replacement.
This safety device is design to prevent water damages that normally occur when the AC drain-line is clogged.
With your purchase you will get the entire SET added or replaced with one, two or three pieces in accordance with the code requirements (Building Code requires different "set ups" in every situations).
NOTE: Photos shows equal or similar item to what you get, with a few examples of how they may look on the system.