Hi GS,
Thanks for sharing your feedback. The RP78 single door set comes with 2 x 2100mm and 1 x 1000mm lengths, the measurements are clearly listed under the specifications tab on the product page.
These sizes fit the vast majority of standard doors, but as some doors can be taller, we always recommend measuring before purchase to make sure you’ll have the right coverage.
If your door is taller than 2100mm, you will likely need to choose a product specification that suits your particular door.
As the RP78 is a screw fixed product, you can unscrew it and fit a more appropriate solution.
We’d be happy to help you work out the right solution so you can get the best draught-proofing result for your home.