Black Heat Shrink Tubing 2:1 Ratio — 0.8mm to 210mm, Cut to Length

Measure the outer diameter (OD) of the wire or bundle you need to cover. Choose a tubing size whose unshrunk diameter is at least 10–20% larger than your wire OD. After shrinking at a 2:1 ratio, the tubing will recover to roughly half its listed diameter. For example, 6mm (≈1/4") unshrunk tubing shrinks to approximately 3mm — ideal for a 2.5–3mm wire bundle. When in doubt, size up slightly; tubing that is too small will not slide over the wire before shrinking.

This tubing uses a 2:1 shrink ratio, meaning it shrinks to approximately half its listed (unshrunk) diameter when heat is applied. For example, 10mm (≈3/8") unshrunk will recover to roughly 5mm (≈3/16"). This ratio is the most common for general-purpose wire insulation and is sufficient for the vast majority of automotive, electronics, and DIY applications.

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 standard heat gun set to low or medium is typically the best tool — move it steadily along the tubing to avoid hot spots. A soldering station with a hot-air attachment also works well for small diameters. Avoid open flames, which can scorch or char the tubing unevenly.

Standard polyolefin heat shrink tubing provides good UV and moisture resistance for general outdoor use — for example, protecting wire splices on garden lighting, trailer wiring, or rooftop antenna cables. For prolonged submersion or harsh marine environments where a fully watertight seal is required, an adhesive-lined (dual-wall) heat shrink tubing is generally recommended, as the inner adhesive layer flows and bonds to the wire jacket during shrinking.

Yes. This black heat shrink tubing is commonly used for automotive wiring repairs, connector insulation, and harness bundling. It is generally rated to withstand the temperature ranges found in passenger compartment and under-dash wiring. For under-hood applications near the engine or exhaust, confirm the operating temperature rating of the specific size you select, or contact us for guidance.

Measure the total length of wire, splice, or connector you need to cover, then add 10–15% extra for overlap and trimming. For a single wire splice, 25–50mm (1–2 inches) of tubing is typically sufficient. For longer cable runs, harness protection, or production use, the 10m, 20m, or 50m options offer the best value per meter. If you are unsure, the 1m or 3m lengths are a cost-effective way to test fit before committing to a larger quantity.

Polyolefin heat shrink tubing in this style is typically rated for up to 600V, which covers the vast majority of low-voltage automotive (12V/24V), marine, and electronics applications. For mains electrical work (120V/240V AC household circuits), this tubing is generally suitable as secondary insulation over already-insulated conductors. For primary insulation on mains wiring or for applications above 600V, please contact us to confirm the appropriate grade before ordering.