The dryer balls use specially designed nodes to physically break down the stiffness created by water drying in fabric, thus softening laundry without the introduction of toxic chemicals.
The two balls have different tensile strengths (one is harder than the other) with different shaped softening nodes. Square nodes compress and soften fabric: round nodes relax fibres to reduce hardness. They work in combination to lift and separate the laundry whilst tumble drying. They also retain the heat and transfer it to the clothes as they tumble, aiding the drying process.