The thoughtful design of the Peridise allows for easy introduction, comfortable use, and a freedom of movement for an experience like no other. Just as its easier to grip a baseball bat than a pencil, the Peridise Beginner Set contains two of our larger devices (22mm and 18mm) and the Advanced Set contains two of our smaller devices (20mm and 16mm). As your skill and strength advances, you should move down in diameter. You will find that the smaller the device, the more exquisite the pleasure.