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Black rubber mastic tape strips in a pack of 40

3M

3M 2229 Mastic Tape 125 mil 3-3/4 x 6-1/2 in PK40 electrician tool

SKU CH-TDGZ-J5CSK

Self-fusing rubber mastic strips insulate up to 1,000 V from 32 to 100 °F, 40 pieces per pack

  • Self-fusing mastic adhesive creates moisture-resistant seals
  • 125 mil rubber backing insulates up to 1 000 V
  • Strips sized 3-3/4 x 6-1/2 in fit common splices
  • Operates reliably from 32 to 100 °F
  • Pack of 40 strips supports multiple jobs

3M 2229 Mastic Tape Strips

This 3M 2229 mastic tape comes as self-fusing strips designed for electrical insulation. Each piece measures 125 mil thick with a rubber backing and mastic adhesive. The pack contains 40 black strips rated for up to 1,000 V. It suits electricians and maintenance crews needing reliable splice protection.

Suits splicing and sealing jobs within the rated

The tape performs between 32 and 100 degrees F, so it fits typical indoor and outdoor electrical work. Buyers who need a thinner tape, a different voltage rating, or continuous rolls instead of pre-cut strips should look at other options. It is not made for high-temperature environments beyond the stated maximum.

Check your voltage and temperature requirements

Verify that your application stays within the 1,000 V limit and the 32 to 100 degrees F operating window. Confirm that pre-cut strips measuring 3-3/4 by 6-1/2 inches match the splice sizes you typically handle. Ensure self-fusing mastic adhesive meets your insulation and moisture-sealing needs.

How it compares

Measured against everything we stock in Electrical Trade Tools & Kits, at today’s prices. Recalculated every night.

Price $245.99
Pricier than about 83% of the 5,006 comparable items (median $95.99).

Specifications

Product
Brand name3M

Questions about this item

What voltage-rated conductors can I seal with the 2229 mastic strips?

Each strip is rated for 1 000 V, so it suits low-voltage automotive and residential circuits up to that level.

Will the tape stay flexible if my garage drops to 32 degrees F?

Yes — the minimum performance temperature is 32 degrees F, and the rubber backing remains pliable down to that point.

How do I confirm the self-fusing bond has formed after wrapping a splice?

The mastic layers merge into a single void-free mass; a firm, uniform feel with no separate layers signals a complete bond.

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