This massager is excellent! Press and hold the power button to set time, green (shortest), orange (middle) red (longest). It has a variety of setting so you can find which setting is best for you. I've used this for almost 2 years and it still works like the first day I received it.Important: Super thick mattresses limit the vibration, I just purchased a new bed. The way I solved the problem was to use two small blankets folded with one vibration module in each blanket, then inserted into a zipping pillow case to hold it together. I set these on the bed next to me and the vibration works great, even better than when I had the modules insert between the mattress and box spring. This saved me, I was so disappointed with the new mattress when I had no vibration to fall asleep. The photo shows the vibration pillows I use on the thick mattress.I purchased two of these units, one is a spare. Once your used to having a vibration bed, going to sleep without it is difficult.Worth every penny and I highly recommend this unit ?