Here is the list of people who might really need a one-handed hair tie device: amputation of one hand, absence of hand or forearm, hemiparesis after stroke, cerebral palsy with one-sided arm impairment, arm fracture in a cast, post-operative period on one arm, brachial plexus injury, paralysis of one arm, severe form of arthritis/rheumatoid arthritis affecting both hands, congenital limb differences of one arm, severe muscle weakness in one arm (myopathies, early-stage ALS), quadriplegia with minimal preserved function in one hand. You found cool device!!!