Do you need new castors for your Grand Executive Lowback? The braked castors are part of the original construction of Grand Executive Lowback. They meet the highest quality standards and are characterised by accuracy of fit. Castors are available for different floor types – hard floors (e.g. wooden floors) and carpets – and are sold individually. In most cases, Vitra recommends replacing all the castors on your product at once to ensure a smooth and consistent rolling movement.