Swivel Armchair Black 5-Star Base With Hard Castors 2D Adjustable Arms height adjustable with options for forward tilt and seat depth adjustment. Promatic option automatically adapts to the users weight and is a perfect chair for muliple users. Chair Type: Office swivel chair with 5-star base (swivel height-adjustable) complying with EN 1335 / Seal of ergonomic approval. Mechanism: Promatic mechanism. Back: Backrest frame of polyamide with ventilated mesh back and adjustable lumbar support. Armrests: 2D