BMW F8X M3/M4 RWS Carbon Fiber DiffuserBMW F8X M3 M4 RWS Carbon Fiber Diffuser The RWS or RW Signatures carbon fiber rear diffuser features a 3 fin design for a modded look without being overly aggressive and in your face. The RWS F8X diffuser is perfect for the customer who wants the unique aggressive carbon fiber diffuser but doesn't want to worry about scraping or getting caught on parking blocks which can be an issue with the larger diffuser options we offer. These RW Signature M3 M4