The blue tumble dryer balls mechanical softeners have different tensile strengths and different shaped softening nodes. They work together in the tumble dryer to mechanically soften fabrics without the harmful chemicals found in fabric softener and dryer sheets. The tumble dryer balls lift and separate the laundry whilst drying, thus reducing drying time and creasing. The tumble-dryer balls softeners also retain the heat and transfer it to the clothes as they tumble, further speeding up the drying process.There is no need to add a chemically laden "softening" dryer sheet or use fabric softener in your wash. Place both dryer balls softeners in the tumble dryer and operate the machine at the usual heatsetting for the fabrics. dryer balls mechanical softeners are re-usable - just leave them in the tumble dryer to get the benefits time and time again!"