2-gang decora and duplex pair box seal
SKU: STC022107

Duplex / Decora Box Seal

$192.00 Bag of 40

$ 4.80 per seal

The Duplex/Decora Box Seal fits NEMA devices and standard size wall plates made by Hubbell, Leviton, Lutron, Mulberry Metal, Pass & Seymour/Legrand. Cooper plates for duplex receptacles are not recommended.

The Duplex/Decora Box Seal is always stocked. Minimum order is a bag of 40. Please allow 2 weeks to fill and ship your order. There is no cost for shipping the Box Seal.



How it Works

Made of neoprene rubber, this wall plate gasket fills the gaps between the plate and the wall surface, and between the outlet box and the wall plate, reducing the amount of sound that travels between rooms.

Installing the Box Seal can improve STC outlet values by 7dB, allowing it attain STC-62 or higher.

Two key qualities make it possible: mass and resilience. The neoprene rubber is dense to block sound, but also resilient so it bounces back to dampen sound energy. Other gaskets and sticky putty pads are made of malleable clay which changes and holds shape due to applied pressure (and sound waves), and doesn’t block sound as effectively as neoprene.

Who Can Use It

Any types of buildings that need to prevent sound traveling between rooms can benefit from the Box Seal.
Image of Residential BuildingsImage of HotelsImage of HospitalsImage of SchoolsImage of RestaurantsImage of Office Spaces

The Benefits

The Box Seal has many benefits over products like sealants and putty pads, including:

  • Lower priced than either putty pads or sealants.
  • Ease of use in existing partitions. Putty pads require the wall to be partially demolished for installation in renovations.
  • Inconspicuous yet easily verified. Wall plates must be removed to verify if sealants are in place; putty pads are unverifiable once the gypsum board is installed.
  • Fire protective as certified by Underwriters’ Laboratories for single duplex outlets, even back-to-back.
  • Simple installation that can be completed by maintenance staff with just a screwdriver.
  • Cleaner and easier, with no messy, sticky clay or putty to deal with.
  • Unlimited shelf life.
  • Unaffected by heat or cold, as opposed to sealants that lose consistency.
  • Less waste, with no half-used tubes of sealant or wrong size putty pads left over.
  • Secure within the outlet box, as they can’t fall into the wall like a putty pad can.
  • L.E.E.D. Credits available for using the Box Seal in schools and healthcare facilities.


To put the Box Seal’s effects into context, you can imagine a typical hotel room, which usually shares a wall with an adjacent room and has five recessed outlets on each side. Most hotel chains’ standards require a minimum STC-50 partition. However, with untreated outlets, the effective performance drops to STC-42.

Using a higher STC wall won’t fix the problem, as sound will still pass through the openings created by the outlet.

But simply installing Box Seal increases the performance of the wall by seven decibels.

STC Performance Benefits

Increased performance by seven decibels in a hotel with five outlets.

Product Testimonials

October 7, 2013

Box Seals

We have gone from weekly, if not daily, complaints to ZERO complaints since completion last April.

April 22, 2016

Blank Box Seal, Blank Pair Box Seal, Decora / Toggle Box Seal

From the last conversation I had with the (customer), everything was exactly as they expected. The STC box seals seemed to have done exactly as intended in terms of sound attenuation.

Frequently Asked Questions

What is the Box Seal made of?

Neoprene, a dense and resilient rubber selected for its ability to isolate vibrations through viscous damping. It is also specially compounded to be Class A fire-rated per ASTM E119.

Will there always be a 7-decibel improvement in sound transmission loss?

Performance will always improve by at least 2-3 dB with the Box Seal and as much as 7 dB. The amount is affected by the STC rating of the partition, number of outlets, and the presence of sound attenuation blankets or putty pads.

Does the Box Seal meet National Electric Code (NFPA 70) requirements?

Yes. The Box Seal spans the wall opening just like the wall plate so that it occupies no space inside the electrical box. Specifically, the requirements of Section 314.16 are unaffected by use of the Box Seal.

What configurations are available?

NEMA configurations used in the United States, Canada, Mexico, Central America, Colombia, Ecuador, Venezuela and most Caribbean and Pacific Islands. Single-gang and 2-gang arrangements are standard for duplex receptacles, toggle switches, Decora-size openings, and data/TV/phone outlets. Custom configurations are available by special order and pricing. Minimum order quantities (MOQ) will apply.

What Color is the Box Seal?

The standard color is light almond. The edge of the seal is an inconspicuous 1/16-inch thick, and the color blends well with light-colored wall plates. The edge can also be painted once installed.Custom colors are available by special order and pricing. Minimum order quantities will apply.

What sizes are available?

Box Seals are made to fit flush to the edge of standard-size wall plates and are recommended. Midsize and oversize plates also fit over the Box Seal. Annular space should not exceed 1/8-inch.

Can the Box Seal be used in a fire-rated partition?

Yes, the Box Seal can be used for existing outlets in fire-rated partitions under any conditions.  For new outlets, compliance with the “24-inch Rule” of the International Building Code (714.3.2) for protecting recessed outlets on opposite sides of a fire-rated partition is commonly required.

Does the Box Seal replace putty pads?

Yes, for fire-rated partitions up to 1-hour for the most common 1-gang duplex configuration. The Box Seal has been tested per UL 1479 and is listed in the Underwriters Laboratories Fire Resistance Directory as a wall opening protective device. Use with a metal wall plate when outlets on opposite sides of a fire-rated partition are less than 24-inches apart.


The Duplex Box Seal is certified by Underwriters Laboratories as wall opening protective material and listed in the UL Fire Resistance Directory CLIV.R38040..

UL Classification logo
In the AIA Product MasterSpec

Section 262726 Wiring Devices as a Wall Plate Gasket.

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