Office Chairs without Arm Rest, or desk chair, is a type of chair that is designed for use at a desk in an office. Office Chairs without Arm Rest is usually a swivel chair, with a set of wheels for mobility and adjustable height. Office Chairs without Arm Rest typically use a single, distinctive load bearing leg (often called a gas lift), which is positioned underneath the chair seat. Near the floor this leg spreads out into several smaller feet, which are often wheeled and called casters. Office chairs were developed around the mid-19th century as more workers spent their shifts sitting at a desk, leading to the adoption of several features not found on other chairs.