3:1 Ratio Adhesive Glue Lined Heat Shrink Tubing – Waterproof Black Heatshrink

Measure the outer diameter of the wire, connector, or object you need to cover. Choose a tubing size whose recovered (shrunk) inner diameter is slightly smaller than your object's diameter. For example, a 9.5mm (3/8") tube recovers to approximately 3.2mm, so it works well on objects up to about 3mm in diameter. When in doubt, size up — you can always shrink tighter, but you can't stretch tubing that's too small.

A 3:1 shrink ratio means the tubing shrinks to one-third of its original supplied diameter when heat is applied. This is significantly more versatile than standard 2:1 tubing, allowing it to fit over larger connectors, irregular shapes, and stepped terminations that a 2:1 tube could not accommodate.

Yes. The inner wall is lined with a thermoplastic adhesive (hot-melt glue) that melts and flows during shrinking, sealing around the substrate to create a watertight, airtight bond. This makes it suitable for marine wiring, outdoor electrical connections, and other moisture-exposed environments.

This dual-wall adhesive tubing typically begins to shrink at around 70°C (158°F) and the adhesive fully activates at approximately 120–135°C (248–275°F). A heat gun is strongly recommended over an open flame for even, controlled shrinking. Always move the heat source continuously to avoid scorching.

Yes. The adhesive-lined construction creates a sealed, corrosion-resistant barrier that is well-suited for outdoor, marine, and automotive environments. The tubing generally offers resistance to UV exposure, moisture, salt spray, and mild chemicals, though performance in extreme conditions should be verified for your specific application.

This tubing is compatible with a wide range of wire gauges and connector types. The available sizes (1.6mm to 65mm supplied diameter) cover everything from fine signal wires to large battery cables and multi-pin connectors. It works with copper, aluminum, and tinned conductors, and is commonly used over butt connectors, ring terminals, and cable splices.

Generally, cut the tubing at least 10–20mm (about 1/2" to 3/4") longer than the area you need to cover on each side. This overlap ensures the adhesive seals fully onto the substrate beyond the connection point. For connectors, the tubing should extend past the connector body on both sides.