Anti-Leak PTFE Pipe Fitting Tape is a soft white tape that is designed to be wrapped around pipe connectors, threads, and under hoses to help prevent leaks.
Whenever you install pipework that uses a hosetail or threaded connector, or use flexi-hose, there are generally tiny gaps present through which water can escape. Wrapping PTFE pipe fitting tape around the connector or thread before you clamp it down with a hose clip can help prevent leaks.