MMR 90mm billet coolant cap for BMW The MMR Performance 90mm billet coolant expansion cap for BM Ws has been designed from the ground up in the UK, constructed from a solid billet of aluminium. Each MMR cap starts life as a solid billet of 6061 aerospace-grade aluminium. It's meticulously machined from this billet with the latest CNC 5-axis technology, before being polished, then gloss-anodised to stay beautiful year after year. All MMR coolant caps arrive pre-sealed and pre-installed with an OE spec valve and internal spring. No need to remove the valve assembly from your OE cap. A true plug and play solution. It has been designed to instantly give your BMW an under-bonnet boost in the aesthetic department, finished in a deep gloss black anodised finish. Never again will you worry whether you tightened your expansion cap fully, as the cap contains complete OE replacement internals. The carefully considered design gives ample surface grip area for your fingers, making installation and filling your coolant that little bit easier. Features Designed and engineered in the UK Crafted from 6061 aerospace-grade aluminium Full OE cap replacement, not just a cover Sophisticated internal springing and bleed off Anodised in MMR signature gloss black Joins existing range of MMR billet caps Pre-installed factory spec Viton O-Ring Additional Information Please note if the part is under excessive heat for prolonged periods of time, it can affect the overall finish, which is unavoidable with anodised aluminium products. Fitting Information All MMR coolant caps arrive pre-sealed and pre-installed with an OE spec valve and internal spring. No need to remove the valve assembly from your OE cap. A true plug and play solution. Vehicle Fitment Series All BMW with matching 17 11 7 639 021 OE part number Chassis code All BMW with matching 17 11 7 639 021 OE part number Model year All BMW with matching 17 11 7 639 021 OE part number Model variant All BMW with matching 17 11 7 639 021 OE part number Engine code All BMW with matching 17 11 7 639 021 OE part number