Complete dimensional, weight, and performance data for the Brass-Seal™ Exterior and Interior Forged Brass Mail Slots and the BOTA Mail Slot Insulator.
Document
BOTA-SPEC-2026
Testing Authority
Intertek
ASTM E283
Patents
Brass-Seal™ System
Patent Pending
Mail Slot Insulator
Two Utility Patents Granted
Year
2026
Contact
spec@blockouttheair.com
blockouttheair.com
Exterior and Interior configurations share identical dimensional and weight specifications.
| Outer Dimensions | 9.88" L × 3.76" W |
| Inner Opening | 8.00" L × 2.25" W |
| Weight | 2.46 lb / 1.12 kg |
| Outer Dimensions | 13.26" L × 4.01" W |
| Inner Opening | 11.375" L × 2.50" W |
| Weight | 3.16 lb / 1.43 kg |
Configuration Notes
Exterior Forged Brass Mail Slot
| Closure | Heat resistant magnetic closure |
| Temperature | Retains approximately 90% pull strength at 212°F — relevant to direct sun exposure on dark or south-facing doors |
| Cavity Gasket | Polyurea-lined |
| Perimeter Gasket | Continuous; between rear of slot and door face |
Interior Forged Brass Mail Slot — Calibrated
| Closure | Calibrated magnetic closure |
| Calibration | Reduced resistance allows mail to pass without bending or damage |
| Cavity Gasket | Polyurea-lined |
| Perimeter Gasket | Continuous; between rear of slot and door face |
PVD Finishes Available
PVD (Physical Vapor Deposition) bonds at molecular level to solid forged brass. Not a surface coating.
Door cut specifications for installation within the door cavity. Horizontal and vertical expansion is fully adjustable within the ranges below.
| Door Cut Width Range | 7.12" – 8.48" |
| Door Cut Height Range | 1.94" – 2.50" |
| Door Cut Width Range | 10.76" – 12.12" |
| Door Cut Height Range | 2.30" – 3.15" |
Installation Notes
| Placement | Installed within the door cavity |
| Installation Method | Tool-free |
| Adjustment | Fully adjustable horizontal and vertical expansion |
| Compatibility | Fits a wide range of mail slot openings and door cutouts within the specified ranges |
| Flap Material | Polyurea — moisture barrier with acoustic properties |
| Door Thickness | Compatible with doors 1.5" and thicker |
| Use Cases | Standalone retrofit, pairing with Exterior Forged Brass Mail Slot, historic properties |
| System Classification | Standalone product — not part of the Brass-Seal™ system |
Specification Note
The Mail Slot Insulator can be paired with the Exterior Forged Brass Mail Slot or used independently as a retrofit solution. It is compatible with historic properties and situations where existing exterior hardware is to remain. It is not classified as part of the Brass-Seal™ system. Contact [email protected] for project-specific specification guidance.
Standard
ASTM E283
Pressure
75 Pa
Wind Equivalent
25 – 30 mph
Testing Authority
Intertek
Units
CFM/ft²
| Configuration | Infiltration (CFM/ft²) |
Exfiltration (CFM/ft²) |
Interpretation |
|---|---|---|---|
| Typical exterior door (code-level) | ~0.30 – 0.50 | ~0.30 – 0.50 | Standard full door performance |
| High-performance exterior door | ≤ 0.30 | ≤ 0.30 | Tight, well-sealed system |
| Conventional mail slot | Not tested | Not tested | Open, unsealed airflow path |
| Exterior Forged Brass Mail Slot (standalone) | 0.20 | 0.11 | Controlled airflow at opening |
| Interior Forged Brass Mail Slot (standalone) | 0.12 | 0.06 | Further reduced air movement |
| Brass-Seal™ System (Exterior + Interior) | 0.20 | 0.11 | Layered system performance under pressure |
Data Interpretation
The Interior Forged Brass Mail Slot performs tighter than the Exterior alone in standalone testing. In a paired system, the Exterior unit is the limiting layer under pressure. System infiltration reflects exterior performance — this is expected and correct behavior in pressure testing.
These results demonstrate that each slot independently controls air movement at the mail slot opening. Do not interpret the system result as a reduction beyond measured exterior values.
Trade & Specification
Trade & Spec
Press
Website
blockouttheair.com
Available on Request
Hi-resolution product photography
BOTA Press Kit 2026
Finish sample reference files
Press releases — blockouttheair.com
Block Out The Air
Defining the New Standard in Brass
Document Type
Technical Specification Sheet
Year
2026