There is no industry standard for mail slot sizes. The BOTA Mail Slot Insulator is available in letter and magazine sizes, and each configuration expands horizontally and vertically to accommodate the range of cutout dimensions within that size category.

Length and width dimensions are listed for each size when selecting the product. Measure your existing mail slot cutout and select the configuration that matches your opening.

The Mail Slot Insulator is built to last the life of the door. The materials were selected specifically for longevity under daily use and seasonal change. BOTA warrants the product against manufacturer defects for 10 years.

The insulator is installed on the interior side of the door where it is not visible from the exterior. Black was selected to remain discreet within the mail slot opening.

Yes. The BOTA Mail Slot Insulator is protected by two granted United States utility patents.

The BOTA Mail Slot Insulator is designed in Denver, Colorado.

When correctly installed, the insulator provides near-complete blockage of air infiltration through the mail slot opening. View the installation video at blockouttheair.com/install for guidance on achieving a proper seal.

The insulator will prevent most insects from entering through the mail slot. Ultra-small insects may still pass through. Insect prevention is not the primary purpose of the product.

The steel closure bar is designed to allow mail to pass through freely while returning to a sealed position after each delivery. The magnets at the base are calibrated to be strong enough to maintain a secure closure but not so strong as to impede normal mail delivery.

The insulator is designed for horizontally oriented mail slots. A vertical installation may be possible in some cases, but the magnetic closure is designed to engage horizontally. You may need to manually reposition the insulator periodically for the magnets to engage properly.

The steel closure bar places a physical barrier between the mail carrier and the interior of the door, protecting both the mail carrier from pets and pets from the mail slot opening. The insulator has been built to withstand most pet contact. BOTA does not warrant damage caused by pets.

Pet damage is not covered under the BOTA warranty. The insulator is built to withstand most pet interaction, but damage caused by animals is considered outside the scope of the manufacturer warranty.

Installation requires no tools. The process involves installing adhesive-backed perimeter foam into the mail slot cutout, placing the insulator in its unexpanded state, and clicking it apart horizontally then vertically until firm against the foam. If an interior mail slot plate is present, it may need to be removed first and reinstalled after.

Most exterior mail slot flaps open within the door cavity. Positioning the insulator toward the interior keeps it clear of the exterior flap's range of motion and ensures a proper seal.

The insulator can accommodate a reasonable degree of variation in the cutout. Minor irregularities in the cut are manageable. Extreme deviations from a standard rectangular opening may affect fit and seal quality.

Yes. The adhesive-backed perimeter foam is included and should be installed into the mail slot cutout before placing the insulator. The foam provides frictional hold to keep the insulator in position and seals any small gaps between the insulator frame and the cutout perimeter.

No. The magnetic closure system is oriented for a specific installation direction. Installing the insulator upside down will prevent the closure from engaging correctly.

The steel closure bar on the flap engages with the magnets at the base of the unit, drawing the flap to a consistent, sealed position after each delivery. The perimeter foam seals the frame to the cutout. Together, they eliminate air gaps at both the flap and the frame perimeter.

Track System Overview

The insulator uses a 9-slot horizontal expansion track. Slot 1 is fully collapsed. Slot 9 is fully expanded. Vertical height is controlled by spring-loaded flat-head screws on the left and right side tracks. Side covers must be removed to access the vertical reset screws.

Part A — Horizontal Reset

/ Insert a flat-head screwdriver into the horizontal track slot and depress the red button straight down.

/ Hold pressure and slide the unit horizontally back to Slot 1 one slot at a time.

/ Confirm the unit is locked in Slot 1 and fully collapsed horizontally.

Part B — Vertical Reset

/ Remove the left and right side covers to expose the silver flat-head screw and spring on each vertical track.

/ Pull each screw head straight toward you (use fingers first, pliers only if needed for access).

/ While holding both screw heads, slide the upper bracket downward to the lowest slot needed.

/ Release both screw heads. The springs will return them to their seated position.

Complete horizontal reset before beginning vertical reset. After both resets, the unit will be fully collapsed and ready for proper installation.

The Brass-Seal™ is a forged brass mail slot system comprising an exterior unit and an interior unit. Each can be specified independently or together as a complete paired system. Both are engineered to seal the mail slot opening and are independently tested under ASTM E283 by Intertek.

The Brass-Seal™ Forged Brass Mail Slot is available in letter and magazine sizes. Magazine size: 13.262" x 4.013" x 0.62" / 3.16 lbs. Letter size: 9.887" x 3.763" x 0.62" / 2.46 lbs.

The Brass-Seal™ system is available in three PVD finishes: Satin Brass, Satin Nickel, and Satin Black. All visible components including screws and hinge pins are finished to match. PVD (Physical Vapor Deposition) bonds the finish at the molecular level. It does not sit on the surface — it becomes part of it.

Forged brass is produced by compressing the grain structure of the brass under pressure, producing a material that is denser, stronger, and more resistant to wear and corrosion than cast or plated alternatives. The Brass-Seal™ system is solid forged brass throughout — not plated, not cast.

The Brass-Seal™ system was independently tested under ASTM E283 by Intertek, one of the world's leading product testing and certification organizations. ASTM E283 is the industry standard for measuring air infiltration through building components under specified pressure differentials. Testing was conducted at 75 Pa, approximately 25 mph wind pressure. Results are on file for specification review.

The exterior unit uses a heat-resistant magnetic closure engineered to maintain consistent compression against the acoustic-lined cavity gasket in high-temperature conditions, including direct sun exposure on dark or south-facing doors. The interior unit uses a calibrated closure designed to allow mail to pass easily while returning to a precise sealed position after each delivery. Both units include a continuous perimeter gasket that seals the hardware to the door face, eliminating hidden air gaps.

Yes. Each unit can be specified independently or together as a complete paired system. The exterior unit can be specified alone to upgrade visible exterior hardware. The interior unit can be specified alone when preserving an existing exterior mail slot. Together, they represent the most complete mail slot upgrade available.

Yes. The Brass-Seal™ Exterior Forged Brass Mail Slot can be paired with the BOTA Mail Slot Insulator for added interior performance at a lower cost than the full paired brass system. The Mail Slot Insulator is not part of the Brass-Seal™ system but is fully compatible as a complementary retrofit solution.

Yes. Both the exterior and interior units feature an acoustic-lined cavity gasket that absorbs impact and softens the transmission of exterior noise. A continuous perimeter gasket between the rear of each unit and the door face eliminates hidden air gaps at the hardware-to-door interface.

Installation uses the included template and matching PVD screws. Position the template level and centered around the door cut-out, mark and drill 7/64" pilot holes, and secure with the provided screws using a Phillips screwdriver. Polish with a soft cloth. Do not use abrasive cleaners. Full bilingual instructions are available for download above.

The Brass-Seal™ system is patent pending. Proprietary sealing engineering developed exclusively by BOTA.

Yes. Specification documentation, material samples, and press assets are available for architects, designers, and editors. Contact info@blockouttheair.com to request.