The seat and front part of the HÅG Conventio 9510's backrest are partially upholstered. The back of the backrest is plastic.Removable seat and backrest covers. HÅG in Balance® technology ensures more subconscious movement.Recessed handle in the backrest for lifting. Dress up the chair for dinner at night with a HÅG SlipCover as an optional extra. Armrests and the HÅG Writing Tablet available as optional extras. The chairs can be stacked fifteen high.