I've had these and the fine and coarse grit sponges sitting on a shelf for years now. I used them once for drywall sanding and didn't think much of them. They are (in my opinion) too small for drywall. Where I discovered they really shine is wet sanding primer. They are holding up very well, hanging onto their grit, cleaning up beautifully. Also make a nice sanding block for backing up the 800 or whatever grit paper.