Hellermann Tyton-Shrin Kit-321-A-Basic-380-03004-Hellermann Tyton-380-03004-P-The-Hellermann Tyton-Shrin Kit-321-A-Basic-is-Dual-Wall-Heat-Shrink-Tubing-with-a-3-1-shrink-ratio-The-attractive-&-reusable-kit-is-ideal-for-assembling-&-identification-The-inner-wall-melts-when-heated-&-is-forced-into-gaps-When-the-tubing-cools-down-the-adhesive-forms-a-seal-preventing-any-moisture-seeping-in-thus-protecting-the-components-The-black-tubes-are-mainly-used-for-the-protection-of-connectors