The m550i exhaust tips are slightly larger than the oem 540i & 530i.
They would fill this M5 style diffuser way better.
https://www.futuredesignusa.com/prod...-rear-diffuser
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2018 M550I Xdrive Alpine White on Cognac Leather, Premium Enhanced Package, Drivers Assitance Plus, Remote Parking/display key, massage seats, 21 wheels style 629 Black Chrome. M performance brakes in blue, M performance carbon fibre diffuser, m performance side skirt extensions, m performance front lip. 45% tint, roof wrapped in gloss black.