The merchandise under consideration is identified as the Stress ReleaZer ST100, which is described as a breathing stone. You state that the subject device is a relaxation aid and breathing trainer. The device is comprised of a plastic housing, measuring 7 inches long by 5 inches wide, containing an electrically vibrating motor, various electrical components, and a rechargeable battery. On the outside of the device is a power button, lights, and a function selection button. In use, the device is held on the chest of the user and, when powered on, provides a vibration and flashing light pattern that are used to time a breathing pattern. Additionally, the user can select to play relaxing tones, including forest, jungle, and ocean sounds, that assist in calming the individual.
[1] Please importantly note that only the relevant portion of the related is displayed above. You may refer to the said customs ruling for the entire ruling explanation.
[1]. https://rulings.cbp.gov/ruling/N322430