NASCAR has made changes to its aero rules for short tracks and road courses in an effort to create "more exciting" races by reducing downforce.
The rear spoiler of the Cup Series car will be reduced from 8-2.75 inches for the nine rounds where the new package will be used.
The splitter overhang is also reduced from 2-0.5 inches, while the overhang part that wraps from the centre of the car around the front corners to the wheels - termed the 'wing' by NASCAR - will reduce to 2 inches, down from 10.5.
Also the radiator has been altered, with the fencing removed to take away front-end downforce.
The changes should make the cars more unpredictable and difficult to drive.
NASCAR's executive vice president and chief racing development officer Steve O'Donnell admitted there was room for "improvements" in the racing on short tracks and road courses.
"Our goal has always been to provide the best possible racing for our fans, regardless of venue," said O'Donnell.
"The 2019 Cup Series race package delivered some of the most exciting races on intermediate and larger tracks that our sport has seen, however we felt we could make improvements to short tracks and road courses.
"We believe we have found the right balance for 2020 that will allow teams to build off their previous knowledge of this package and showcase exciting side-by-side racing at tracks of all sizes."
The new package will be used at Bristol, Dover, Martinsville, New Hampshire, Phoenix, Richmond and road courses Charlotte Roval, Sonoma and Watkins Glen.