Tokyo, Japan - A wise old-school engineer once said that the acid test for a custom component was that it should make the original it replaces look like an aftermarket add-on.
Well, we reckon the aero and trim kit on this M4 from BMW specialists 3D Design in Tokyo passes the ultimate test; its smooth styling, perfectly matching lines, and show-class fit and finish makes a standard M4 look just a little dated.
This could be next year's factory special from the M skunk works in Munich.
The kit has been engineered to fit both the M3 and M4, comprising a suspension lowering kit and carbon-fibre front splitter, rear diffuser, boot-lid spoiler, side skirts and mirror housings - which, to our surprise, some customers opt to leave out.
The show car's interior has also been treated to some 3D Design trim tweaks - check the gallery for some cute branding.