SWRBM-57 | radio replacement With SWC retention for Mercedes, BMW, Porsche & smart vehicles the Crux SWRBM-57 is a multi-can radio replacement interface for select Mercedes-Benz, BMW, Porsche & smart vehicles. It facilitates the integration of an aftermarket radio to retain factory features with can-bus based vehicles. This enhanced interface is also pre-programmed for retention of steering wheel controls. This kit includes both quad lock and ISO harnesses