If it is all getting a little confusing then get back to basics with the actual upvc letterbox sizes you need for our standard replacement upvc letterboxes. If you are measuring the aperture through the door then the sizes here will help you as will the fixing detail. So the task is to get the plastic letterbox sleeve through the aperture that has been cut in your upvc door. Remember to ensure the fixing positions are usable or workable as well.

Buy a 10 Inch uPVC Letterbox

10 inch upvc letterbox sizes

replacement sizes for replacement 10 inch upvc letterbox

Buy a 12 Inch uPVC Letterbox

12 inch upvc letterbox sizes

replacement sizes for 12 inch upvc letterbox

Buy a 12 inch Slimline uPVC Letterbox

12 inch slimline upvc letterbox sizes

replacement sizes for 12 inch narrow letterbox

Help Guide For uPVC Letterbox Screws (Does not apply to 12 inch Slimline Model)

Take care not to assume the letterbox screw is the same size as the door thickness. The thing to note is that the screws pass into a lug which protrudes from the outer side of the letterbox. The letterbox screws shown below are wood type screws (No.8). When you first screw these into the outer side of the letterbox use a bit of force to get the self-tapping screw to engage. Once the screw starts to thread it will cut the thread into the lug much more easily. Do be careful that you have the correct screw length. If it is too long it will come out the other end of the lug you are screwing into. This applies to the standard models for the 10 inch letterbox for upvc door and the 12 inch letterbox for upvc door. We have a short video to show you how to fit a upvc letterbox if it helps at this stage.

 Door Thickness (mm)

uPVC Letterbox Screw Size (mm)
 22-27  Purchase 32mm Screws
 28-33  Screws Supplied
 34-39  Purchase 44mm Screws
 40-45  Purchase 50mm Screws
 46-51  Purchase 57mm Screws
 52-57  Screws Supplied
 58-64  Not Available
 65-70  Purchase 76mm Screws