According to human acupoint design 39pcs acupoint massage balls for each foot.<br> <br><b>What is the Benefit of our Massage Slipper? </b><br>1. Promote blood circulation and metabolism <br>2. Release aches pain such as headaches, migraines, neck pain, lower and upper backaches. <br>3. Get rid of body's wastes and toxins<br> 4. Relax nerve tension, improve sleep quality<br> <br><b>What is the difference of our massage slipper with others? </b><br>1. our massage slipper using rotating massage head, which is 360 degree rotating massage. NOT UP AND DOWN ONLY<br> 2. our massage slipper added 2pcs jade stone, 2pcs tourmaline stone for health therapy<br> 3. our massage slipper used environmental materials (no heavy smell). ROHS certificate approved <br><br><b>Size Reference:</b><br> S- 10.04inch long(Men's size 6-8, Women's size 7-9.5) <br>M-10.826inch long(Men8.5-10.5, Women10-12) <br>L- 11.614nch long(Men11-13)<br>If you are between sizes, take larger one<br><br><b>P.S:</b><br>This is acupressure massage slipper, if you are looking for a comfortable all day wear slipper, please DON'T buy it. <br>You may feel painful for first several days, wearing socks and shorten the wearing time will help you feel better. <br>Gradually increase the wearing time after you get used to this foot massage, you will get the benefit soon.