Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A saddle chair uses the same principles in its design as an equestrian saddle. It does not have a backrest but is equipped with a chair base on castors and a gas cylinder for adjusting the correct sitting height. The castors enable moving around and reaching out for e.g. tools while sitting. Riding-like sitting on a saddle chair differs from the one on a conventional chair. Saddle chair users sit 20-30 cm higher, which puts the hips and the knees into a 135º angle, compared to the 90º angle typically associated with sitting on a traditional chair.