The lid has reinforced edges at the front and back

Mountain Pass Performance's own words about their suspension arms for the Model 3:

Citroen DS5 2011–2015

Why should you buy the Audi S3/A3 S-line 8V Hatchback/Sportback Back Side Splits

it also increases the air pressure on the front axle

Rear side splitters bmw 3 touring e91 Mazda 6Mk2 The lid has reinforced edgesRear Side Splitters BMW 3 Touring E91 Suitable: BMW 3 Touring E91 20042008 Complete set contains: Splitters (left + right) Splits are in black color, it is ready for mounting. No need for further work, unless you want to paint it for a different color. Splitter visually lowers the car and improves the grip and the stability of the vehicle. In addition, you can choose red or white stripe for self assembly. (By default we send the product without any