A uniquely shaped rocker (the eccentric bicylinder) sits just under the seat of every QOR360 chair. Because this rocker is curved on both its upper and lower surfaces with the curves at right angles to one another, this rocker allows the seat of a QOR360 chair to tip in every direction. So, while the geometry of the rocker is simple, the healthy motion it encourages is quite sophisticated. If you purchased an adjustable chair, arrange for the seat top to be even with the top of your kneecap. The height of one’s chair is very important to allow you to take full advantage of our active chairs. We recommend that you measure the distance from floor to the top of your kneecap (patella) while standing and then pick the chair with a height closest to your personal patellar height. If you find yourself between sizes, it’s a good idea to choose the larger size. The fit doesn’t have to be exact, but you should select the chair that most closely fits your personal anatomy.