a balance board for recreational purposes, enjoying the challenge that this equipment presents. Circus skill The balance board is used as a circus skill for recreation and performance. Many circus performers refer to the balance board as the rola bola. Skillful and dramatic balancing acts using the rola bola are performed by circus performers in traditional circus as well as by freelance circus skills artists. The performance can involve a single rola bola or a stack of multiple rola bolas on top of one another to increase the challenge and visual spectacle. Some circus performers also combine the use of the rola bola with other circus skills such as juggling or equilibristics to present a different visual spectacle. Structure The user stands on a board or other platform which is on top of an unstable ground-contacting member, the fulcrum. The height of the fulcrum of most models is between 3 and 6 inches (i.e., the top of the fulcrum is that distance above the ground). Due to the fulcrum's instability, the user must remain balanced and coordinated in order to prevent the board from touching the ground. Thus, the rider stimulates, exercises and teaches the parts of the body that implement the act of balancing (toes, soles, ankles, knees, hips, shoulders, arms and neck) and the parts of the body and brain that create the sense of balance and that engineer the implementation of the act of balancing (inner ears, cerebellum, proprioceptors and eyes). The degrees of movement through which the board can move – sliding, pivoting, rotating, tilting, rolling or some combination of those – and the speed of the board differ in different types and subtypes of models, depending on the shape and size of the fulcrum, whether it is attached to the board and, if it isn't attached, the method(s) by which it is constrained by the board, if any. With an increase of speed and with each additional degree of movement through which one model or another can move, the need to avoid losing control of the board forces the rider to exercise considerably more skill in order to avoid falling. In rocker boards and wobble boards, the fulcrum is attached to the board. In rocker-roller boards and sphere-and-ring boards, the fulcrum is a separate piece from the board. In sphere-and-ring boards, the fulcrum (an inflatable or solid ball) is constrained by a ring on the