This is the Vulcanized black rubber tape 19mm [F5340101] Vulcanized butyl rubber. Coalesces into a homogeneous mass within hours. Should be protected by a soft plastic tape/electrical tape at the risk of abrasion or impact of UV light. With protective liner. For waterproof splicing of cables and protection against corrosion of pipes. Also as moisture protection to electrical components. ...Contact us if you need more help.