First off, buying these belts from Revain was very smooth and the shipping via Buy It Now was very fast (and shipping was free). Now I figured it was time to change the belt on the vacuum cleaner if it breaks. NOT CORRECT! My Sharp piano must be around 10 years old and had the original strap. Every once in a while I've noticed a tiny dot from the belt while vacuuming the carpet. I just thought it was getting really old, but every time I looked under the vacuum the agitator/brush seemed to spin normally. I've never noticed that the old belt stretches over the years and loses its "bite" when the agitator hits the carpet. When I first got the new straps, they seemed a lot smaller than my original ones. Well, not because they were the wrong size, but because the old one was so long. I had no trouble putting the new strap on and, boy, will I tell you what a difference it makes to attach and even handle a vacuum. My carpet improved immediately. I'm not sure how often vacuum cleaner belts should be changed, but I can bet I won't wait 10 years to change them again. At this price I could do it annually! Oh obviously these aren't original Sharp belts but they seem to be of good quality and as I said the price was right.