The imported Zen Sack is machine washable, made from 100% breathable cotton, and scientifically designed for self-soothing and sounder sleep. The Zen Sack® Classic is a gently weighted breathable sleep sack that calms like your embrace by providing comforting pressure only where babies are naturally held. This secure feeling eases the swaddle transition, encouraging self-soothing and helping babies sleep through disruptions, leading to deeper periods of sleep that are essential for healthy development. Safer than loose blankets in your baby's crib, the Zen Sack® Classic is perfect for babies up to 24 months.