This is a faucet plug with a nylon brush on the end.
This handy little extra has the potential to make your beer dispensing cleaner and easier. It’s just a simple plug that fits into the faucet to keep insects, mold, and other unwanted things out of the faucet when it is not in use.

Do not forget to remove the plug before opening the tap.

California Proposition 65

Proposition 65 Warning: This product contains chemicals known to the State of California to cause cancer and/or birth defects or other reproductive harm.