Heat Shrink Tubing 3:1 Ratio — 0.8mm to 40mm, Multiple Colors & Lengths

Measure the outer diameter of the wire or connector you need to cover, then choose a tubing size whose recovered (shrunk) diameter is slightly smaller than that measurement. Because this tubing has a 3:1 shrink ratio, the recovered diameter is typically one-third of the supplied diameter. For example, a 6mm (≈1/4") supplied tube generally recovers to about 2mm (≈5/64"). When in doubt, size up one step to allow easy insertion before shrinking.

A 3:1 shrink ratio means the tubing will shrink to approximately one-third of its original supplied diameter when heat is applied. This is generally double the shrinkage of standard 2:1 tubing, making it well-suited for irregular shapes, connectors, and applications where a tighter, more conforming fit is needed — such as stepped terminals or multi-conductor bundles.

This tubing typically begins to shrink at around 70–90°C (158–194°F) and fully recovers at approximately 120°C (248°F). A heat gun is the recommended tool — move it slowly and evenly along the tubing to avoid hot spots. Avoid open flames, which can scorch or burn the tubing unevenly.

Once fully shrunk, the tubing generally provides a snug, moisture-resistant seal around the covered surface, making it suitable for many outdoor electrical connections and marine wiring applications. For fully waterproof or submersion-rated applications, contact us to confirm the specific variant meets your requirements before ordering.

The range of supplied diameters (0.8mm to 40mm) covers wire gauges from very fine signal wires up to large power cables and multi-pin connectors. In most cases, the supplied diameter should be larger than the object being covered so the tubing slides on easily before shrinking. Contact us if you need help matching a specific AWG gauge or connector body size.

Yes. The tubing can be cut to any length with scissors or a utility knife before applying heat. Cut cleanly and squarely to avoid fraying at the ends. The 1m, 2m, and 5m length options let you stock the right amount for your project without waste — the 5m roll is particularly cost-effective for wire harness repair work.

No — the color options (Black, White, Red, Blue, Yellow, Grey) are purely for identification and organization purposes. All colors share the same 3:1 shrink ratio and electrical insulation properties. Color-coding is commonly used in automotive wiring, panel builds, and multi-circuit installations to distinguish circuits at a glance without additional labeling.