My favorite by far, have used many, are the 9224 Ultimate Outer 2.5 Record Sleeves. These are not only great quality but also very reasonably priced. If you wait a bit, Sleevecity tends to having 10% and sometimes 15% off sales. Just go to their website and you will see if there is a sale currently going on. Here's the link:
www.sleevecityusa.com
Then search for the 9224 sleeves....no affiliation by the way, just a very satisfied customer and I also really enjoy their inner sleeves. I use the 9235 Diskeeper 2.0 for more ordinary albums and the 312NLPS for my more valuable album inner sleeves.