Here are my new Sweet Cheeks 100% wool dryer balls scented with Pink Sugar (smells like cotton candy). Dryer balls are simply reusable balls that replace your dryer sheets or liquid fabric softener. They can be made of plastic or wool. I have a set of plastic, but now that's it's winter I need a couple more to keep the static down. There isn't an exact number that you have to have but I think the drier your climate is the more balls you need. I have four total now. I have been using dryer balls instead of fabric softener sheets since May 2010. The Pink Sugar scent is wonderful, it makes the whole house smell like cotton candy.