These dryer balls are 100% wool and contain no dyes or chemicals. They reduce drying time, soften and fluff fabric and reduce static. When you add dryer balls into your dryer, the balls will get in between the towels and clothing. The dryer balls will separate and pull them apart with their weight. This will allow more of the hot air in and around your laundry helping the dryer to heat your clothes more quickly and remove the evaporated water out of the dryer more efficiently. Just add your favourite essential oil blend for a light, fresh scent. We recommend using 3 dryer balls. These last around 1 year depending on usage.