PET film water-blocking tape is a type of electrical tape used for water-blocking in communication cables, fiber optic cables, and power cables. It is made of PET film and coated with a water-blocking adhesive on one side. The tape is used to prevent water ingress into the cable and protect the electrical components from moisture damage. The water-blocking adhesive swells in the presence of moisture, which seals off the cable from water and prevents further water ingress. The PET film also provides electrical insulation properties and physical protection for the cable. PET film water-blocking tape is commonly used in the telecommunications and power industries.