It's water tape! I used it around my very old shower faucet where I wanted to install a detachable shower head. I tried installing the head without tape, but the water just flowed out of where the fitting touched the head. I applied a very small amount of tape (about two coats) around the fitting and reinstalled the head. Water no longer drips out of the nozzle. That was about 2 months ago and still no problems.