Ergo Ergo active stool.

Great stool for an office, classroom or to add an eccentric pop of color to your space. Approximately 20 inches tall and 16 inches wide. Description from website: Practice active sitting with the ExtraErgo Stool. Whether you're working or relaxing, the ErgoErgo is perfect in the office, studio, or classroom, or anywhere else comfortable, compact seating is needed. The stool encourages movement and activates your core for better concentration and improved posture. The ExtraErgo compresses slightly to the height of a standard chair when you sit on it. Adjust it by tilting the stool or scooting backwards or forwards. The ExtraErgo offers all the benefits of the ErgoErgo, but it has a larger seat for taller people and more stability for a range of body types. It's perfect for people from 5 feet 7" to 6 feet 4" tall and can hold up to 250 lb.