The SystemOne Machine UI Knob is dark, charcoal gray in color with a silver rim on the top. The sides of the knob flare out slightly and are ridged for easy gripping. It comes standard with all SystemOne 60 SERIES CPAP/BiPAP machines. It can also be used to replace the lighter gray Machine UI Knob found on all SystemOne 50 SERIES CPAP/BiPAP machines