Laundry balls are a product made of solid, insoluble material promoted as a substitute for laundry detergent. They are different from dryer balls, which are used in the dryer to help prevent clothing from clumping and wrinkling, as well as reduce drying time. Laundry balls are often marketed as an economical and environmentally friendly alternative to laundry detergent, but their effectiveness is debated. Producers of laundry balls often make pseudoscientific claims about their mechanisms of action and exaggerate the extent of their benefits. Washing with laundry balls is as effective or less effective than washing without detergent. Their observed cleaning effects can largely be attributed to the mechanical interactions with the laundry or to using hot water instead of cold. In contrast, dryer balls are effective in reducing drying times, preventing clumps in laundry, and reducing wrinkles and static cling. They are most commonly made of tightly compressed wool, but can also be made of plastic or rubber. They work by tumbling between layers of fabric and separating them, allowing warm air to circulate better and reducing drying time. The movement of the dryer balls against fabrics can also help fight wrinkles, prevent static, and soften clothes.