I was watching a vid on McGuire-she has a guest today Ricky Bromero. (who runs a card drive for animal charity also)
Anyway-at 10:45 he shares a trick for card sellers someone gave him and I thought it was worthwhile to mention. People may have already figured this out. I had not.
It allows you to put it in without closing it. So if you have an inside sentiment it is visible. People dont have to open the card. You pop in the envie too. Seal it. And then you can fold it closed so the size stays true.
This one only works for long side opening A2. (6 x 9 sleeve) We might find more sleeves that allow for other sizes or openings. You get them on AZ from a seller called Spartan.
https://www.youtube.com/watch?v=9LaR-0aIuls
There are sleeves that are like book jackets one can get but it will not fully cover the card inside that I have seen yet. (still better than nothing)