Black Heat Shrink Tubing 2:1 — 20mm to 210mm Large Diameter, 20cm Piece

Measure the outer diameter of your cable bundle, conduit, or pipe end. Choose a heat shrink size where the expanded inner diameter is at least 10–20% larger than your cable. With a 2:1 shrink ratio, the tubing shrinks to approximately half its listed diameter after heat is applied. For example, 40mm tubing shrinks to approximately 20mm. When in doubt, size up — a slightly oversized tube will still shrink down tightly.

A 2:1 shrink ratio means the tubing shrinks to approximately half its original expanded diameter when heat is applied evenly. For large diameters, this is especially important: 100mm tubing shrinks to approximately 50mm, and 210mm tubing shrinks to approximately 105mm. Always verify your cable or conduit dimensions against the selected variant before ordering.

Black polyolefin heat shrink tubing generally offers better UV resistance than clear or colored variants, making it suitable for light outdoor use including sealing conduit ends, protecting outdoor cable splices, and covering pipe joints in electrical enclosures. For long-term direct UV exposure, submersion, or direct burial applications, additional weatherproofing measures are typically recommended. Contact us to confirm suitability for your specific outdoor environment.

A heat gun with adjustable temperature settings is strongly recommended for all sizes in this range (20mm–210mm). Apply heat in a slow, even sweeping motion from the center outward to avoid trapping air or creating wrinkles. For very large diameters (100mm and above), work slowly and methodically around the full circumference. A lighter or hair dryer is not recommended for these sizes — they do not provide sufficient or even heat for large-diameter tubing.

Yes. Polyolefin heat shrink tubing is generally electrically insulating and is widely used for insulating large cable splices, sealing conduit ends, and protecting exposed conductors in industrial and marine electrical installations. Always verify the voltage rating is appropriate for your specific application before use. Contact us if you need confirmation of the dielectric rating for a particular use case.

Each piece is 20cm (approx. 7.9") long before shrinking. This is typically sufficient for sealing a single conduit end, covering a cable splice, or capping a pipe joint. If you need longer coverage, you can order multiple pieces and overlap them slightly for a continuous seal. For continuous long-run coverage, consider our cut-to-length heat shrink tubing listings available in 1M–25M lengths.

This large-diameter black heat shrink tubing is typically used for sealing and protecting conduit ends and pipe joints in outdoor electrical enclosures, covering large cable bundle splices in industrial and marine wiring, providing strain relief and abrasion protection on thick power cables and battery leads, capping the ends of cable trays and conduit runs in commercial electrical work, and protecting large-diameter hoses and tubing in automotive and industrial applications. The 210mm option is particularly suited to very large conduit or pipe end sealing.