Two points
If it has an aluminum threshhold it is adjustable.
I use a 3/4" solid closed cell foam for the bottom gasket and the new closed cell door gasket from
Scamp for the door.
The 3/4" foam has worked well since installed 13 years ago.
It is also available in 1" which would work as well.
The last two pictures show first the threshold gasket and then the door gasket.