I have washed a jelly roll in mesh laundry bags because I intended to use it for a jelly roll race quilt where the exact measurements don't really matter. I've also washed a charm pack from which I cut appliques, so any shrinkage didn't matter on that front either. Don't know if I'd wash if I needed the exact 2.5" or 5" for a specific pattern. The packaging does say not to wash.