Free size. It relieves foot muscle tension and provides whole-body relaxation by acupressure and magnetic therapy. It applies reflexology and acupressure to the entire of your foot from the toes to the soles. The rotating balls press into the pressure points on the bottom of your feet which, in turn, affects your whole body. Each ball is contrived to apply a maximum effect with minimal effort! It increases the fitness and efficiency of the body. It also helps to cure many problems like high blood pressure, diabetes, headaches, and many more health problems. Instruction for Use: wear the slippers for 10 minutes in the morning as you prepare for work or other activities. Stimulate nerve endings and increase blood flow to the body, they also help eliminate retained water and toxins. No electric charge is required. The dual benefit of Spring Acupressure & Magnet Therapy is reduced pain in the lower and upper back, neck, shoulders, hips, muscles & joints. If the pressure of the spring nodes is intense at first, wear a pair of socks while using them until your feet become accustomed to the stimulation.