Durable construction and finish. Padded seat, filled with a durable material that will not rot or decay over time in heat or cold. Adjustable height - with a reach broad enough to put an observer at a comfortable position for a variety of telescope eyepiece heights. Ability to fold into a compact, ideally flat profile. Good lateral stability - so that if an observer leans left or right the chair will not easily tip over. Good quality materials, resistant to rust or corrosion.