Cushy cork. The Sway Stool, designed by New York designer Daniel Michalik, flexes when sat upon... Here's the description from Branch: The central column of the stool, located directly under the spine of the user, is flexible, solid cork while the rest is perforated. The result is a seat that flexes and pivots under the weight of the user, responding to the slightest body movement. The user's muscles remain slightly engaged to maintain balance, improving posture and circulation. Many have reported this to be a perfect seat for working at a desk or computer, enabling the user to move and rock while working and thinking. Because cork is 100% waterproof and impervious to rot and mold growth, this piece functions as well outdoors as it does in.