I had an issue with my door sweep because it had a 1/4" gap between the brush edge and the bottom frame......, mosquitoes/ants loved the opening. The OEM door sweep is part of the screen door frame and don't recall how it was attached..., but I know it's not adjustable. I couldn't find a replacement source at that time.
I purchased a standard vinyl door sweep and cut length to suit, leaving the existing brush door sweep in place......., no more gap.
One like this:
https://www.homedepot.com/p/Frost-Ki...01BH/100194335
Bob
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2016 GM 2500HD 6.0L/4.10
2018 Jay Flight 24RBS
2002 GM 2500HD 6.0L/4:10 (retired)
2005 Jayco Eagle 278FBS (retired)
1999 Jayco Eagle 246FB (retired)
Reese HP Dual Cam (Strait-Line)