100% Natural sheep wool without added fillers, felted into tight balls (just over tennis ball size). This pack contains 2 balls that will last 1000+ loads. When you start your dryer with a load of wet laundry, the items will initially stick together and flop around for a while until the layers become dry enough to separate. These dryer balls work their way in between items as they tumble, allowing the warm air to circulate more efficiently, drying your clothes faster.