This is a HellermannTyton adhesive-lined heat shrink end cap from their standard POX (Polyolefin Cross Linked) sleeving series, designed to seal and terminate cable ends with permanent bonding upon heating to 135°C. Installation involves sliding the cap onto a cable and applying heat to activate the internal adhesive, creating a waterproof, insulated termination. Critical verification: confirm the 20mm inside diameter matches your cable outer diameter before shrinking, as the final shrunk diameter of 7.5mm is irreversible.