MMX 90mm Billet Coolant Expansion Cap for BMW B58 & B57

The MMX 90mm Billet Coolant Expansion Cap has been designed from the ground up in the UK and machined from a solid billet of aluminium, giving a genuine functional upgrade over the factory plastic cap rather than just a cosmetic cover.

Each cap is engineered as a direct replacement for the OE cap, matching OE part number 17 11 7 639 021, and fits BMW models powered by the B58 and B57 engines.

• Machined from solid billet aluminium
• Direct OE replacement — matches OE part 17 11 7 639 021
• Fits BMW B58 & B57 engine applications
• Genuine functional replacement, not just a cover