Letterbox draught excluders: aperture and plate sizes

A flap changes more than the appearance

The two Stormguard examples below are interior products. The version with a flap has a different stated aperture and overall plate size from the no-flap version. Keep the exact article number attached to every dimension when comparing offers.

Measure the opening and the cover separately

The aperture is the opening through which post passes. The overall size is the outside footprint of the cover. Measure both, together with the available flat door-face area and any neighbouring handle, panel or trim. A plate that visually overlaps the opening can still have an unsuitable internal brush opening.

For a hypothetical comparison, a 270 × 40 mm aperture is larger than the stated 254 × 39 mm aperture of 06SR031. Its 292 × 75 mm overall footprint therefore cannot be used as evidence that it fits that opening. Overall coverage and supported aperture size are separate checks; this example does not certify the alternative product either.

Use the fitting drawing for fixings

Both product pages show pre-drilled fixing holes and link their own fitting instructions. The overall width does not establish hole spacing or screw suitability for an existing door. Compare the exact drawing and permitted attachment method before reusing an old fixing position.

The 06SR031 product has a hinged flap over the twin brushes; 06SR017 has no flap. Check the space needed by the moving flap and inspect how the existing letterbox operates. Do not treat an interior brush cover as a complete replacement exterior letterbox or an exterior weather seal.

Choose an exact listing identity

Take the article number, supported aperture, overall dimensions, finish and flap choice to the Amazon listing. Confirm the selected variation rather than assuming every colour or related offer is the same format. Check pack contents and required fixings against the manufacturer instructions.

Use the door-bottom or window reference if the draught comes from another opening. These interior examples provide a concrete size comparison; they do not establish fire-door suitability, permitted alterations to your door or a measured reduction in heating costs.