Heat Shrink Tubing 2:1 Ratio — Black Electrical Cable Sleeving, 2mm–8mm Diameter

Measure the outer diameter of the wire or bundle you need to cover, then choose a tubing size that is generally 20–30% larger than that measurement before shrinking. With a 2:1 shrink ratio, the tubing will typically shrink to half its expanded diameter. For example, 4mm tubing will shrink down to approximately 2mm (≈5/64"). When in doubt, size up — it's easier to work with a slightly larger tube than one that won't slide over the connector.

A 2:1 shrink ratio means the tubing will shrink to approximately half its original expanded diameter when heat is applied. This is the most common ratio for general electrical insulation and wire bundling applications. For example, 8mm (≈5/16") expanded tubing will shrink to approximately 4mm (≈5/32") after heating.

This tubing generally begins to shrink at around 90°C (194°F) and reaches full shrinkage at approximately 120°C (248°F). A heat gun is the recommended tool for even, controlled application. Move the heat gun slowly along the length of the tubing to avoid scorching. A lighter can work for very short sections but may produce uneven results or discoloration.

Polyolefin heat shrink tubing generally provides good resistance to moisture and UV exposure, making it suitable for short-term outdoor use and most automotive wiring repairs. For long-term outdoor, marine, or underhood applications where a fully waterproof seal is required, an adhesive-lined (dual-wall) heat shrink variant is typically recommended. This standard single-wall tubing is well suited for interior automotive wiring harnesses and protected outdoor runs.

The available diameters (2mm–8mm expanded) are generally compatible with wire gauges from approximately 28 AWG up to 6 AWG, as well as small wire bundles and connectors. As a general guide: 2mm suits very fine wires (around 24–28 AWG), 4mm–4.5mm suits mid-range gauges (around 14–18 AWG), and 8mm is suitable for heavier wires or small bundles. Always verify the expanded diameter against your wire's actual outer diameter before ordering.

Available lengths range from 1M (≈3.3 ft) to 20M (≈65.6 ft). For small repairs or single connector insulation jobs, 1M–2M is usually sufficient. For wiring harness builds, vehicle restorations, or workshop stock, 5M–20M rolls offer better value per meter and reduce the need for frequent reordering. Cut to any length with standard scissors before applying heat.

Yes. Polyolefin heat shrink tubing of this type is generally manufactured to be flame-retardant, meaning it will typically self-extinguish when the heat source is removed rather than continuing to burn. It is also electrically insulating, making it suitable for covering wire splices, terminals, and connectors. For specific voltage ratings applicable to your installation, please contact us to confirm.