3-to-1 heat shrink is a semi-flexible tube which possesses a melt-able inner lining. The inner lining is adhesive which flows when heated to ensure complete sealing. How does that help? This offers insulation and mechanical protection needed in electrical connections. As an added bonus, 3-to-1 also provides a moisture-proof seal.
Heavy wall heat shrink is coated internally with a dual purpose thermoplastic liner. This liner flows and encapsulates when heated. The benefit of this is a sealed, tough connection. When cooled, the tubing offers the mechanical strength of a superior adhesive. It also offers the corrosion protection of a high quality mastic. Remember, when choosing a size, you should consider any components or connectors that need covering.