4" NECK TENSION & HEADACHE RELIEF WHEEL: Designed to mimic a masseuses hands pressing gently against the suboccipital trigger points in the back of your head and neck area Massages the suboccipital trigger points in the back of your neck, releasing tension on your neck and shoulders This will reverse the effects of tech neck and will make you feel much better than you do right now WARRANTY & DETAILS: Includes a 10 year manufacturer warranty against defects Each wheel can support up to 500 lbs.