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NSi Industries Metacaulk Fire-Rated Putty Pad
The NSi Industries Metacaulk Fire-Rated Putty Pad is engineered to maintain the hourly fire rating of rated walls that contain electrical outlet boxes, while also reducing sound transmission between adjoining spaces. Sized 7" x 7" x 1/8", this single pad thickness is all that is required to achieve a 1 or 2-hour fire rating, so electricians do not need to add extra putty to plug the end of each electrical metallic tube (EMT) or conduit at its connection to the box. The pad also carries an STC rating of 60, tested in a UL 411 wall assembly/section to ASTM E90, making it a practical choice wherever fire-stopping and acoustic performance both matter. Applied by hand, the pad adheres to common interior building surfaces and installs quickly around outlet boxes during rough-in or retrofit work.
Key Features
- Pad Size: 7" x 7" x 1/8" thickness, sized to fully cover standard electrical outlet boxes in rated wall assemblies.
- Single-Layer Fire Rating: Only one pad thickness (1/8") is required to achieve a 1 or 2-hour fire rating, simplifying installation and inspection.
- Sound Attenuation: Delivers an STC rating of 60, tested in a UL 411 wall assembly/section to ASTM E90 for documented acoustic performance.
- No Additional Putty Required: Seals the end of each EMT or conduit at its connection to the box without the need for supplemental fire-stop material.
- Asbestos-Free Formula: Manufactured with no asbestos fillers, supporting safer handling on the job site.
- Easy Hand Application: Applied entirely by hand and adheres to all common building surfaces for interior use, with no special tools required.
- RectorSeal Brand Manufacturing: Produced under the RectorSeal brand within the NSi Industries portfolio of code-compliant firestop products.
Certifications & Compliance
- Tested in a UL 411 wall assembly/section to ASTM E90
- STC Rating of 60
- No Asbestos Fillers
Technical Specifications
- WARRANTY: 1 Year
- Country of Origin: United States
- Packaging: 1 ea
- Pad Dimensions: 7" x 7" x 1/8"
- Sound Transmission Class: STC 60
Typical Applications
- Fire-Rated Wall Assemblies Containing Electrical Outlet Boxes
- Sound Attenuation Between Adjoining Rooms and Units
- Commercial and Multi-Family Construction
- Renovation and New Construction Projects
- EMT and Conduit Terminations at Outlet Box Connections
- Multi-Family and Hospitality Fire- and Sound-Rated Partitions
Why NSi Industries?
NSi Industries backs the Metacaulk line of firestop products with materials engineered specifically for code-driven fire- and sound-rated construction. This putty pad is formulated without asbestos fillers and is tested in a UL 411 wall assembly/section to ASTM E90, giving electrical contractors and inspectors documented performance data to support fire-rated wall assemblies. Manufactured under the RectorSeal brand and backed by a 1-year warranty, it offers dependable, code-compliant protection for outlet boxes in rated partitions.
Manufacturer Resources
Product Specs
- Sub Division:
- Electrical-E H2
- Division:
- Electrical H1
- Country Of Origin:
- United States
- Warranty:
- 1 Year
- Product Type:
- Putty Pad
- Listing:
- UL 411 Tested (ASTM E90)
- Department:
- Electrical
- Product Group:
- Boxes & Enclosures
- Product Subgroup:
- Enclosure Accessories
NSi 66335 – Frequently Asked Questions
1) Do I need two layers of putty pad to get a 2-hour fire rating on an outlet box?
No. One 1/8 inch thickness of the NSi Metacaulk putty pad is all that's required to achieve a 1 or 2-hour rating in a rated wall containing an electrical outlet box. There's no double-wrapping and nothing to build up, which also keeps the inspection simple.
2) Will a 7 x 7 inch putty pad cover a standard single-gang electrical box?
The pad measures 7 x 7 x 1/8 inches and is sized to fully cover standard electrical outlet boxes in rated wall assemblies. It's applied by hand, so you wrap the back and sides of the box and press the material into place around the knockouts.
3) Do I still have to putty the end of the EMT where it enters the box?
No separate plug of putty is needed. The Metacaulk pad seals the end of each EMT or conduit at its connection to the box, so you aren't buying supplemental firestop material to finish each termination.
4) Will a putty pad actually help with noise between apartment units, or just fire?
Both. The Metacaulk pad carries an STC rating of 60, tested in a UL 411 wall assembly/section to ASTM E90. That's why it gets specified on multi-family and hospitality partitions where back-to-back outlet boxes are the weak point for sound transmission as well as fire.
5) Can I add putty pads to boxes in an existing rated wall, or is this rough-in only?
Either. The pad installs around outlet boxes during rough-in or on retrofit work, and it adheres to common interior building surfaces. No tools, no cure time, no mixing, which is what makes it workable from the room side when you're correcting boxes an inspector flagged.
6) Does this putty pad contain asbestos?
No. The Metacaulk putty pad is formulated with no asbestos fillers, which matters for handling and for facility submittals on healthcare and school work.
7) How many pads come in a pack, and is this made in the USA?
Packaging is 1 each, so quantity ordered equals the number of boxes you can wrap. Country of origin is the United States, which is the detail that usually decides a government or institutional order.
8) Is this an interior-only product?
Yes, the Metacaulk putty pad is specified for interior use and adheres to all common interior building surfaces. Use it on rated partitions in commercial, multi-family, and hospitality construction, not on exterior exposed applications.
How fast can I get the NSi 66335 delivered?
Most orders ship the same day from our distribution partners, with quick delivery throughout the
continental
U.S.
Need it urgently? Contact Us for expedited shipping options.
Can I return it if it doesn’t work for me?
Yes—ZenSupply offers a hassle-free return policy. If the product isn’t the right fit,
reach out to our support team for a return authorization or setup a return by following our return instructions.
Does the NSi 66335 come with a warranty?
Absolutely. The NSi 66335 is backed by a manufacturer’s warranty.
For full warranty terms, check the product documentation or Contact Us.
How do I get technical support or installation help for the NSi 66335?
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