This is a TPU replacement rubber cap for the GAME 14030-BB Solar Digital Pool & Spa Thermometer after the leak fix - see my Amazon review for the problem and fix. This TPU cap is optional, but a good idea for reducing damage risk to the unit.
Print it in a flexible material that is water tolerant, such as TPU. It is snug on the thermometer end. Zip-tie it in place.
Amazon review:
The author hasn't provided the model origin yet.