Magflap® MK3 Horizontal Letterbox Draught Excluder - Stop Draughts, Noise & Heat Loss with Magnetic Seal Technology

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Stop Letterbox Draughts, Noise & Heat Loss Forever Your letterbox is the largest uninsulated hole in your front door. The Magflap MK3 Horizontal is a premium internal letterbox dra ught excluder that uses precision-engineered magnetic seal technology to eliminate draughts, reduce noise, prevent dust infiltration, and improve your home's thermal efficiency. Unlike traditional brush-based letterbox seals that wear out and leave gaps, the Magflap MK3's all-steel construction and brushless magnetic design maintains a perfect airtight seal for decades. Designed and manufactured in Leicester, UK since 2009, the Magflap MK3 Horizontal fits standard 70mm aperture letterboxes and can be installed internally or externally in under 10 minutes with no specialist tools required. Choose from Brass Effect, Black, Silver, or White powder-coated finishes to match your door furniture. Optional locking keyset available for anti-tamper security. --- Why Choose Magflap MK3 Horizontal Over Cheap Brush Excluders? Magnetic Seal Technology - The Magman Difference Traditional letterbox draught excluders use bristles, brushes, or gravity-dependent flaps that leave gaps around the edges. These wear out within 12-18 months, requiring replacement. The Magflap MK3 uses precision-balanced neodymium magnets to create a complete perimeter seal when closed. Post delivery simply pushes the magnetic disc open - it self-closes immediately after, maintaining 100% draught protection 24/7. Brushless Design - No Worn Bristles, No Gaps Brush-based letterbox seals degrade rapidly. Postmen push through thousands of times per year, flattening bristles and creating draught channels. The Magflap MK3 has zero bristles - the smooth magnetic seal never wears out. Our customers report Magflap MK2 units still working perfectly after 15+ years. The all-metal construction outlasts plastic alternatives by decades. Wind-Resistant Engineering Standard letterbox flaps rattle and bang in high winds, waking you at night. The magnetic seal on the Magflap MK3 holds firm under pressure. Silent operation means no more letterbox rattling on windy nights. Internal or External Fitting - Your Choice Install the Magflap MK3 internally for a clean exterior appearance and added security, or externally to protect against driving rain and draughts from outside. The 18mm rear gasket add-on (optional) provides clearance over protruding bolts, nuts, or uneven door surfaces, making installation possible on virtually any UK door. Thermal Efficiency - Reduce Heating Bills An unsealed letterbox loses significant heat. Thermal imaging studies show temperature drops of 5-8°C through standard brush excluders during winter. The Magflap MK3's airtight magnetic seal prevents this heat loss, reducing your heating costs and improving home comfort. Fits UK Building Regulations for thermal performance. UK Handmade Quality - Family Business Since 2009 Every Magflap is hand-assembled in Leicester by our small family-run team. We use British steel, high-quality powder coating, and precision engineering. Supporting Magman means supporting UK manufacturing, fair wages, and quality craftsmanship over mass-produced imports. --- Technical Specifications Dimensions:- External plate: 274mm width × 78mm height × 7mm depth- Internal depth clearance: 10mm standard (28mm with optional gasket)- Letterbox aperture fit: 70mm height (standard UK size)- Weight: 450g (all-steel construction) Materials:- Body: Cold-rolled steel with powder-coated finish- Magnets: Neodymium rare-earth (N42 grade)- Gaskets: Cork (eco-friendly, 99% recyclable)- Hinge mechanism: Stainless steel pivot pins Finish Options:- Brass Effect (powder-coated, low-sheen)- Satin Black (smooth matte)- Silver/Satin Chrome (brushed appearance)- Powder Coated White (RAL 9016 equivalent) Compatibility:- Door types: Timber, uPVC, composite, metal- Letterbox types: Standard horizontal UK letterboxes with 70mm aperture- Bolt clearance: 10mm standard / 28mm with optional rear gasket- Orientation: Horizontal apertures only (see Magflap MK3 Vertical for portrait letterboxes) Add-Ons Available:- Internal locking keyset (prevents letterbox fishing)- Rear gasket (+18mm bolt clearance)- Replacement cork seals --- How to Install Magflap MK3 Horizontal (10-Minute DIY Guide) What You'll Need:- Phillips screwdriver (PZ2/No.2)- Pencil for marking- Level (optional but recommended)- The Magflap MK3 kit includes all fixings Internal Installation (Most Common): 1. Remove existing letterbox flap (if fitted) Unscrew internal cover or brush seal if present. Clean internal letterbox surround with cloth to ensure smooth Magflap operation. 2. Position the Magflap MK3 internally Hold the Magflap against the inside of your door, centered over the letterbox aperture. The magnetic disc should hang freely. Use a level to ensure horizontal alignment. 3. Mark fixing holes Use pencil to mark the four screw holes through the Magflap mounting plate. Remove unit and prepare for drilling if needed (most UK doors allow direct screw fixing). 4. Secure with screws Align Magflap over marked holes. Insert provided screws through mounting plate and tighten with screwdriver. DO NOT overtighten - snug fit only. 5. Test operation Push magnetic disc open (as postman would) and release. It should self-close smoothly and seal completely. Adjust screw tightness if binding occurs. External Installation:Follow same process but mount on exterior door face. Recommend external installation for:- Maximum draught protection from outside winds- Doors with complex internal letterbox mechanisms- Period properties where internal aesthetics matter Troubleshooting:- Disc won't close: Loosen screws slightly - overtightening can bind the pivot- Bolt clearance needed: Use optional 18mm rear gasket to raise unit off door surface- Existing bolts protruding: Rear gasket clears up to 28mm total Full video installation guide available at www.magman.uk/pages/fitting-guide --- Magflap MK3 vs Alternatives - Why Spend £39.99? vs Brush Letterbox Seals (£5-15) Brush seals are the cheapest option but worst performing:- Bristles flatten within 12-18 months (replacement needed)- Gaps around edges allow draughts through- Post delivery often gets stuck in bristles- Plastic construction cracks in cold weather- Absorb moisture and dust (hygiene issues) Magflap MK3 advantages:+ Lasts 10-15+ years (proven with MK2 units from 2009)+ Zero bristles = zero wear+ Complete perimeter seal (no gaps)+ All-steel construction (never cracks)+ 99% recyclable materials Cost Analysis: Brush seal: £10 every 18 months = £60 over 10 years + labourMagflap MK3: £39.99 once = £39.99 over 10 yearsYOU SAVE £20 over 10 years + avoid repeated fitting hassle --- vs Gravity-Dependent Internal Flaps (£15-25) Standard internal flaps (hinged plastic or metal) rely on gravity:- Rattle in wind (noisy at night)- Springs weaken over time (seal fails)- Only work horizontally (not vertical letterboxes)- Plastic versions crack/yellow over time Magflap MK3 advantages:+ Magnetic seal = silent operation (no rattling)+ No springs to weaken+ Wind-resistant up to 60mph+ Premium steel construction (never yellows)+ 1-year warranty vs no warranty --- vs External Letterbox Hoods (£40-80) External hoods protect from rain but:- Expensive (£40-80)- Alter door appearance significantly- Require external mounting (rental property issues)- Don't seal draughts from inside Magflap MK3 advantages:+ Can fit internally (invisible from outside)+ Can fit externally if preferred (£39.99 vs £60+ hoods)+ Seals both internal draughts AND external wind+ Removable for rental properties (4 screws)+ Made in UK with 1-year warranty --- Real Customer Use Cases Period Properties & Listed BuildingsVictorian and Edwardian homes often have oversized original letterboxes (70mm+ apertures). The Magflap MK3 maintains period character externally while providing modern thermal efficiency internally. Brass Effect finish matches traditional door furniture. Removable installation complies with conservation restrictions. Rental PropertiesThe Magflap MK3 is tenant-friendly - no permanent modifications, just four screw holes that fill easily when moving. Take your Magflap to your next rental or return it to Magman for refurbishment and reinstallation credit. New Builds & Passive HousesNew build thermal regulations require airtight construction. The Magflap MK3's magnetic seal meets Building Regulations Part L thermal performance standards. Often specified by architects for Passivhaus projects. Rural & Coastal HomesHigh wind areas need robust letterbox sealing. Customers in Scottish Highlands, Welsh coast, and exposed rural locations report the Magflap MK3 eliminates whistling draughts and letterbox banging that cheaper solutions couldn't stop. --- UK Manufacturing & Sustainability Made in Leicester Since 2009Every Magflap is hand-assembled by our family team in the East Midlands. We support British steel suppliers, local powder coating specialists, and UK packaging companies. Your purchase supports fair wages and quality UK manufacturing. 99% Recyclable Materials- Steel body: 100% recyclable- Cork gaskets: Biodegradable, renewable material (reduces plastic use)- Neodymium magnets: Recoverable and reusable- Spray coating: Zero VOC, environmentally friendly- Packaging: Recycled cardboard, minimal plastic 1-Year Manufacturer WarrantyWe stand behind our craftsmanship. If manufacturing defects occur within 1 years, we'll repair or replace your Magflap free of charge. After 1 years, we offer refurbishment service (clean, repaint, replace gaskets) for £15. Refurbishment ProgrammeMoving house? Send your used Magflap back to us for refurbishment. We'll clean, repaint, and replace gaskets, then offer installation credit toward your next order. Extending product life = reducing waste. --- Frequently Asked Questions Q: Will this fit my 70mm aperture letterbox?A: Yes. The Magflap MK3 Horizontal is designed for standard UK 70mm height letterboxes (landscape orientation). Measure your letterbox aperture height - if it's 70mm (±3mm), the MK3 will fit perfectly. For portrait orientation letterboxes, see our Magflap MK3 Vertical model. Q: Can I install this on a uPVC door?A: Absolutely. The Magflap MK3 fits timber, uPVC, composite, and metal doors. For uPVC, use the provided self-tapping screws (included). Pre-drill 2mm pilot holes to prevent cracking. Q: Will post get stuck in the magnetic seal?A: No. The magnetic disc opens easily when post is pushed through (exactly like your current letterbox flap). The magnets are balanced to allow smooth post delivery while maintaining airtight seal when closed. Postmen report no delivery issues. Q: How strong is the magnetic seal?A: The neodymium magnets create a firm seal that prevents draughts and wind noise, but opens easily for post. Wind tunnel testing shows seal integrity up to 60mph winds. Strong enough to stop draughts, not so strong it blocks post. Q: Do I need the optional rear gasket?A: Only if your existing letterbox bolts protrude more than 10mm from the door surface. The rear gasket adds 18mm clearance (28mm total), allowing Magflap installation over protruding nuts, bolts, or uneven surfaces. Most standard UK doors don't need it. Q: What's the difference between MK2 and MK3?A: MK3 improvements include:- Thicker 1.5mm steel body (MK2 was 1.2mm)- Enhanced powder coating process (more durable)- Cork gaskets instead of rubber (eco-friendly, longer-lasting)- Optional locking keyset compatibility- Improved hinge mechanism (smoother operation)See our full [MK2 vs MK3 comparison guide](#) for details. Q: Can I lock the Magflap to prevent letterbox fishing?A: Yes, with the optional Internal Locking Keyset add-on. This allows manual locking from inside - preventing thieves from reaching through to unlock door latches or fish for keys. Q: Is this suitable for external door mounting?A: Yes. The powder-coated steel and sealed pivot mechanism withstand UK weather. We recommend external mounting for maximum draught protection in exposed locations. The finish will patina naturally over time (similar to all exterior door furniture). Q: What if it doesn't fit my letterbox?A: Free UK returns within 30 days. Measure your letterbox aperture before ordering - the MK3 Horizontal requires 70mm height apertures. If your aperture is different, contact us for custom sizing advice or consider our other models. Q: How long does it take to install?A: 10 minutes average for DIY installation. You'll need a Phillips screwdriver (No.2/PZ2). No drilling required on most UK doors - screws fix directly into timber or uPVC. Watch our [fitting guide video] for step-by-step instructions. Q: Will this work on a vertical/portrait letterbox?A: No, the MK3 Horizontal is designed for landscape orientation letterboxes only. For portrait/vertical letterboxes, you need the [Magflap MK3 Vertical] which uses the same magnetic technology but sized for vertical apertures. Q: Does it come with a warranty?A: 1-year manufacturer warranty covering defects in materials or workmanship. After warranty period, we offer refurbishment service (£15) to clean, repaint, and replace gaskets - extending product life indefinitely. Q: How do I choose the right finish?A: Match your existing door furniture for cohesive appearance:- Brass Effect: Pairs with brass handles, knockers, letterbox plates- Satin Black: Modern, contemporary doors or matte black hardware- Silver: Chrome or brushed nickel handles, modern minimalist aesthetic- White: uPVC white doors, Scandinavian minimalist style Unsure? Brass Effect is our most popular finish (complements most UK door styles). --- What's Included in the Box + 1× Magflap MK3 Horizontal unit (chosen finish)+ 6× Mounting screws (appropriate for door type)+ Cork perimeter gasket (pre-installed)+ Installation instructions+ 1-year warranty Optional Add-Ons (Selected at Checkout):• Internal locking keyset with 2 keys• Rear gasket for bolt clearance (+18mm) --- Specifications at a Glance | Feature | Specification || Aperture Fit | 70mm x 290mm height (standard UK horizontal letterbox) || Dimensions | 274mm W × 78mm H × 7mm D || Weight | 900g || Material | All-steel construction || Finish Options | Brass Effect, Black, Silver, White || Installation | Internal or external || Tools Required | Phillips screwdriver (No.2/PZ2) || Installation Time | 10 minutes average || Wind Resistance | Tested to 60mph || Warranty | 1 year manufacturer || Made In | Leicester, UK || Recyclability | 99% recyclable materials || Compatibility | Timber, uPVC, composite, metal doors | - Order Your Magflap MK3 Horizontal Today + Stop draughts, noise & heat loss permanently+ Brushless magnetic seal technology lasts decades+ 10-minute DIY installation, no specialist tools+ Made in UK since 2009, 1-year warranty+ Free UK delivery & 30-day returns [Add to Cart - £39.99] --- Customer Rating: 4.78 (59 verified reviews) *"Outstanding manufacturing quality rarely seen these days, worth every penny." - Mr John B Young* *"Completely draft proof! Worth it for a really draft-proof door." - Amazon Customer* PAT PENDING Show more