I've had several different covers on my trucks over the years and they've all leaked to some extent. About the best you can say is they keep things dryish.
I ended up selling my factory tri-fold and bought an ARE fiberglass trunk lid love it and everthing is dry as a bone! Got for 400 bucks on craigslist .sold factory one for 200.
Like a colander! And if u look in the owners manual it states to cover valuable items because cover will leak! That was a $850.00 option in 2016 for Tacoma.
Its now $1000 for 2021 Tacoma. I was hoping they put it in wrong. I'm going in for service and will see if maybe they can tighten it down. Not holding out much hope.