I bought wool balls from Amazon to try. Have used them off and on, but they are noisy compared to not using them. I have not timed dryer loads, but I can't see that they have reduced dryer times significantly for us. They do get "lost" in dryer loads of sheets -- especially king size and/or bottom sheets. I have never used dryer sheets. I just use Downey or vinegar in the washing machines, and that seems to take care of static for us. I quit using the wool balls just because I couldn't see that they were worth using for us. In the past I have also tried tennis balls and the spiky plastic balls. My home dryer is small, so that might make a difference.