Brush vs magnetic letterbox draught excluders
A brush excluder costs a few pounds at any DIY shop. A magnetic one costs about £40. Both go over your letterbox and let the post through, so is the difference worth paying for? Here is how they compare, and when a brush is all you need.
The short answer: a brush slows a draught down but never fully stops it, because air passes between the bristles and the bristles wear as post is pushed through. A magnetic flap closes tight against a seal after every delivery. If your letterbox is in a windy spot or a room you want warm, magnetic is worth it. If you just want a cheap improvement for now, a brush is better than nothing.
How each one works
Brush excluder
Two rows of nylon bristles meet in the middle of the letterbox. Post pushes the bristles apart and they spring back.
Magnetic excluder
A hinged steel flap covers the letterbox. Post pushes it open, then magnets pull it shut against a seal. The Magflap MK3 works this way.
Side by side
| Brush | Magnetic (Magflap MK3) | |
|---|---|---|
| Typical price | About £5–£10 | From £41.99 |
| Seal when closed | Air passes between and around the bristles | Flap is pulled tight against a cork seal |
| After a year of post | Bristles flatten, splay or part in the middle | No bristles; the magnets close it the same way every time |
| In strong wind | Bristles move, and some air and noise get through | Magnets hold the flap shut, so it doesn't rattle |
| Post delivery | Thick post can catch, and bristles can mark envelopes | Post pushes the flap open and it closes behind it |
| Materials | Usually plastic frame and nylon bristles | All steel, powder coated, in 4 finishes |
| Fitting | Screws or sticky pads, a few minutes | Screws on, about 10 minutes |
When a brush is the right choice
Choose a brush if
- you rent and want something cheap you can leave behind
- the letterbox is in a porch or sheltered spot
- you only need a quick fix for one winter
Choose magnetic if
- you can feel cold air or hear wind through the letterbox
- the letterbox rattles or bangs at night
- you've already worn out a brush or two
- you want it to look like part of the door
Will a magnetic excluder fit my door?
For the Magflap MK3 Horizontal, the hole in your door must fit inside the 340 × 100mm plate, with flat door all round it. It fits wood, composite, metal and uPVC doors (on uPVC, fit it inside). If bolts stick out behind your letterbox by more than 9mm, choose the additional gasket, which clears 18mm. Upright letterboxes need the Magflap MK3 Vertical.
Print the free full-size fit template to check, or email a photo of your letterbox to info@magman.uk.
Magflap MK3 Horizontal
Made in Leicester since 2009. Rated 4.89 out of 5 across more than 419 reviews.
From £41.99 · Free UK delivery · Free 30-day returns · 1-year guarantee
See the Magflap MK3Compare all excluder typesQuestions people ask
Can I fit a magnetic excluder over an old brush?
Take the brush off first. The Magflap needs flat door around the letterbox to seal against.
Will the magnets stop the postman?
No. The flap opens with a light push and closes on its own once the post is through.
What if I don't like it?
Returns are free within 30 days, and every Magflap has a 1-year guarantee.
What about the keyhole?
A mortice keyhole lets a draught through too. The Mini Magflap covers it with the same magnetic flap, and it's £3 off when you buy it with a Magflap.