You switch between seating styles by flipping this continuously curved geometry.
"The double curved geometry incorporates the ergonomic demands and generates at the same time the necessary stability. Due to the weight of the user the chair adapts slightly in shape and absorbs the impact of the actual forces. TriWing is produced in a digital worlflow and is customized to individual parameters like weight, height and length of leg." (marcohemmerling.com)
More info: marcohemmerling.com