This Balboa kit assembly mount sensor is installed in the spa shell. It allows a 3/8" (9.5 mm) diameter sensor to be mounted directly into the spa shell so that the sensor is in contact with the water.
The lock nut can be adjusted depending on the thickness of your spa shell.
Length: 45 mm
Outside diameter of the face visible from inside the spa: 41 mm
Inside diameter of the sensor gland: 9 mm