You may now choose a clover-shaped swivel base so you can spin around as needed – or roll around as desired if you opt for caster wheels – after you've chosen the Harbour Chair shell style that will be hugging and supporting your body. The base is offered in three finishes: polished aluminum, powder-coated aluminum in black or light grey, and swivel with return options. For improved sitting comfort, all Harbour Chairs have been upgraded with more foam in the seat, which has been increased from 15 mm to 25 mm in thickness.