"In this Product Series, I document the initial development of the 1:1 Carbon Mirror Replacement Caps with Karbonius back in 2020. I discuss the prototype, my first impressions and its eventual discontinuation in 2023.

In 2025, I have set out to create a new option for sourcing 1:1 replica of the original BMW Performance caps. 

This entry looks back at the intention behind this crowdfunding project along with the prototype development with Karbonius in 2021."
- Matt

The beginning of the end. 

BMW M GbmH has recently begun discontinuing the M Performance product line for the E9X M3 starting with one of it's most sought after product: the carbon fiber replacement mirror caps. 

The SKUs 51162157880 and 51162157813 were last available for approximately 425 USD per cap, and 850 USD per set. 

The Alibaba replicas do not adequately replicate the quality of the original BMW Performance units. They are most often manufactured with ill fitting brackets, carbon overlays using the wrong weave patterns and low quality clear coats that rapidly decay when exposed to the elements. 

Close but not quite. 

I reached out to Karbonius Composites back in December 2020. Most known for their E46 M3 products, they had started expanding their catalog to the E9x M3. 

Their initial design were using a OEM ABS mirror cap with a pre-preg overlay. As such, it also used the original plastic brackets and clips for installation.

The original BMW M Performance units were made using a negative mold to create mirror caps purely out of carbon with fewer clips. Only 4x brackets remained on the underside. 

The BMW Performance caps were also thinner than the original plastic caps. This lead to a visually unappealing edge.

Karbonius laid their pre-preg carbon in a "split" design that separated the upper and lower part of the mirror cap. The original BMW Performance caps had continuous weave.

The revised prototypes. 

Working with Ana at Karbonius, she was able to convince the product team to revise the design to the original M Performance specifications. A new mold was created along with revised

Karbonius and I got together to develop a brand new set of 1:1 M Performance style replacement mirror caps with the added bonus of 1x1 weave option, matching the OEM CF roof by BMW M GmbH.

The new caps were entirely made from pre-preg carbon without any added fiberglass or the original ABS plastic structure. 

The caps were developed with 3D printed OEM style brackets matching the original position of the BMW Performance units.

Karbonius matched the continuous 2x2 weave pattern as seen below. 

Up next: I test fit the prototype and look back at the crowdfunding process & production.