Rear
154 products
Carbon fiber rear aero parts for BMW M cars and selected Audi, Mercedes-AMG and Tesla models, from diffusers to full trunk lids. The back of the car is covered here: diffusers and bumper corners for the lower bumper, spoilers and wings for the trunk, tailgate or roof, and replacement trunks with the lip built in.
The biggest choice is for the G80 M3, G82/G83 M4 and G87 M2, including rear parts Unit 17 designs itself. Parts for current models are mostly pre-preg dry carbon, while some older listings only say carbon fiber, so read the material line on each product. Unsure what suits your car? Text a photo to 609-525-4865.
Rear buying guide
Diffuser, spoiler or trunk: what each one changes
A diffuser fills the lower part of the rear bumper around the exhausts. Many for current cars replace the factory plastic part on its own mounting points, and on the M3 and M4 you can also swap the gloss-black bumper corners and outer trim for carbon. A spoiler changes the profile from the side: a low lip, a ducktail, a roof spoiler on an SUV or wagon, or a wing on stands. Compare styles under Spoilers / Wings. A trunk is the biggest step, because it replaces the whole lid. See Trunks for the G87 M2, G80 M3 and G82 M4 versions.
Planning a matched carbon rear end
Style names help you pair parts. MP style follows BMW M Performance shapes, while CS and CSL styles borrow from BMW's lightweight specials: the M3 CS left the factory with a carbon rear spoiler and diffuser, and the M4 CSL with a carbon trunk lid that has the spoiler built in. A CSL-style trunk already has its lip, so it takes the place of a trunk spoiler rather than pairing with one. On the G80 and G82, Unit 17's 3-piece diffuser already comes with rear corner extensions.
Fitment checks before you order
- Body style. An M3 sedan, M4 coupe and M4 convertible each have their own trunk, so spoilers, trunks and rear corners come in separate versions.
- LCI or pre-LCI. The X3M/X4M SQ-style diffusers are listed for the facelift (LCI) only, while the Unit 17 X3M diffuser fits both but not the X4M.
- Exhausts and bumper. Diffusers for older 3, 4 and 5 Series cars are made for one bumper type (M Sport or SE) and one exhaust layout.
- Tow hitch, sensors and lights. One X3M diffuser won't clear the factory tow hitch, some sets need the parking-sensor carriers moved over, and diffusers with a brake light need wiring.
How rear parts go on
Methods vary by listing. Many trunk spoilers use pre-applied 3M tape with no drilling. Most current diffusers bolt to the factory points, but a few need the bumper off, for example to wire an F1-style light. Older listings for earlier models often come pre-drilled with self-tapping screws, which means drilling your bumper or trunk. Test-fit every part before you paint, drill or install it: if it doesn't fit the car named on its product page, tell us before installing and our fitment guarantee covers the return shipping.
Frequently asked questions
Should I start with a rear diffuser or a trunk spoiler?
It depends on what bothers you when you look at the car. A spoiler changes the side profile and is usually the easier job, since many fit with 3M tape. A diffuser changes the view from behind and pairs naturally with carbon rear corners, but it often means working under the bumper. If you want the whole look in one step, a CSL-style trunk plus a diffuser covers both.
What does 3-piece mean on a rear diffuser?
A center diffuser plus two outer pieces that carry the line around the bumper corners. The Unit 17 X3M set is a 3-piece diffuser with rear corner splitters, the G87 M2 3-piece wraps around the exhausts, and the X5M set follows the bumper around to the sides. Each listing shows what is in the box.
Which rear parts are body-specific on the G80 M3 and G82 M4?
Trunks, trunk spoilers and the replacement rear corners come in separate M3 and M4 versions, because the sedan and coupe rears differ. The MP-style diffuser, the outer diffuser trim and our 3-piece diffuser are listed for the G80, G82 and G83. Browse by car on the G82/G83 M4 page to see only what fits.
Are these rear parts sold for Audi and Mercedes too?
Yes. There are diffusers and spoilers for the Audi RS3 (8Y), RS6 Avant (C8), S3, S5 and first-generation R8, and for the Mercedes C63 (W204 and W205), C43 and G-Class, plus a diffuser for the 2024 Tesla Model Y Long Range. The Audi RS3 range includes Unit 17 designs such as the RD1 Pro diffuser and the S2 Pro and SD2 Pro spoilers.
Can I return a spoiler or diffuser after fitting it?
No. Parts that have been installed, drilled or painted can't be returned, which is why we ask you to test-fit first. Uninstalled parts in their original packaging can come back within 14 days of delivery for a refund, excluding shipping. Full terms are in our return policy.