Perforated vent holes cover the butterfly-shaped back panel, so warm air escapes instead of building up against your shirt through an afternoon of work. The panel itself curves to the spine, and integrated armrests carry the elbows without adding width beyond 25 inches. Seat height runs 17.5 to 20 inches from a lever under the seat; unlock the tilt and the back rocks between 100 and 117 degrees, then swivels a full 360 degrees. The U-shaped seat measures 19 by 18 inches and is packed with high-density sponge that holds its shape rather than compressing into a dish. A gas cylinder handles the lift, and the base is rated for 330 lbs. Overall the chair occupies 25 by 24.5 inches, reaches 38 to 40.5 inches tall and weighs just 21 lbs. A breathable butterfly-shaped backrest is the main visual and functional feature of this ergonomic desk chair. Seat size: 19" x 18"