3:1 Ratio Heat Shrink Tubing – Black Electrical Wire Sleeving (Without Glue)

Measure the outside diameter of the wire or bundle you need to cover. Choose a heat shrink size whose inside diameter (before shrinking) is typically 1.2–1.5× the bundle diameter. After applying heat, the tubing shrinks to approximately one-third of its original inside diameter, creating a snug fit. For example, a φ9mm tube suits a bundle up to about 6–7mm in diameter.

A 3:1 shrink ratio means the tubing shrinks to roughly one-third of its original inside diameter when heat is applied. For example, a φ9mm tube will shrink down to approximately φ3mm, providing a tighter, more secure fit than standard 2:1 tubing — making it suitable for irregular shapes, stepped connectors, and larger bundles.

This polyolefin heat shrink tubing generally begins to shrink at around 70–90°C (158–194°F) and fully recovers at approximately 120°C (248°F). A heat gun is recommended for even, controlled shrinkage. Avoid open flames, which can scorch or unevenly shrink the tubing.

Yes. This tubing is made from flame-retardant polyolefin, which generally offers good resistance to UV exposure, moisture, and common automotive fluids. It is typically rated for continuous use in temperatures ranging from approximately -55°C to +125°C (-67°F to +257°F), making it suitable for engine bays, marine wiring, and outdoor electrical installations.

No. This is a non-adhesive (without glue) heat shrink tubing. It provides mechanical protection and insulation through a tight physical fit after shrinking. If you need a waterproof seal or adhesive bond, consider a dual-wall adhesive-lined heat shrink tubing instead.

Sizing varies by wire insulation thickness, but as a general guide: φ1.5mm suits very fine wires (typically 28–24 AWG); φ3mm suits 22–18 AWG; φ4.5–6mm suits 16–14 AWG; φ9–12mm suits 12–10 AWG or small bundles; φ15–24mm suits medium cable bundles; φ30–50mm suits large harnesses or conduit. Always measure your bundle before ordering.

This non-adhesive tubing provides moisture resistance through a snug mechanical fit, but it is not fully waterproof on its own. For submersion or high-moisture environments, an adhesive-lined dual-wall heat shrink is generally recommended. For above-deck marine wiring and connector protection, this tubing is typically adequate.

For a single splice or terminal, you generally need 20–50mm (≈1–2") of tubing. For a full automotive harness repair or workshop project, 5–10 meters is typically sufficient for most tasks. Larger rolls (15–50 m) are cost-effective for workshops, electricians, or anyone doing ongoing wiring work.