We designed ZipString with safety in mind: First, the string has very little mass, making it safe to touch while moving. Second, the circuit constantly monitors motor torque, so if anything unusual happens, it shuts off automatically. Finally, the string loop is designed to break if it encounters excessive tension, keeping things safe during play. There's also battery safety and protection circuitry. The wheels are smooth so hair slides in and out without tangling. ZipString is certified from the highest standards across the toy industry.