These are the greatest invention yet.  I was not sure how these were going to work as I fluffed up the first duster, but after the initial swipe on an old bookcase (with a layer of dust) I was astonished.  It picked up all of the dust and left the bookcase clean, with no dust remaining, not steaks, nothing.  Then I went around to find the more challenging things to clean and every single one of them cleaned up extremely well.   I used each "cloth" until it began to fall apart, they lasted so long .