I just LOVE LOVE LOVE these tiles!!!! I used them to create a mirrored backsplash for my bar. I didn't sand or prime or anything, I just stuck them to the existing painted wall - hence the "use extra adhesive". They are SUPER sticky, and I am betting that if I had not been sticking them to a gloss painted and textured wall, I wouldn't have needed the extra adhesive. I used Loctite spray adhesive in a line down the center of each and it worked like a dream. These are incredibly easy for DIY projects.