There have been many versions of the Mercedes-Benz SLR McLaren over the years - from the iconic 722 Edition to the stunning Stirling Moss - but none quite like this. Here we have what is probably the most special SLR to date: the Mercedes-Benz SLR McLaren MSO HDK. And not just any HDK - this is Volcano, the last of only 12 units ever made by McLaren Special Operations (MSO), and easily the most extreme road-going version of the SLR to date - surpassed only by the track-only 722 GT.
The road-going 722 GT
The HDK - which stands for High Downforce Kit - is McLaren Special Operations’ ultimate homage to the 722 GT. That was a wild prototype race car built under Gordon Murray’s watchful eye that never actually raced but served as a proof of concept to show what the SLR could do in a motorsport setting. The 722 GT was hardcore, raw, and rare - only 21 units were built, all track-only. The HDK brings that race-bred DNA to the street.
MSO didn't hold back. The HDK bodywork is a completely reimagined take on the SLR, featuring extensive carbon fiber components like the front lip, hood insert, rear diffuser, and that gigantic rear wing. Compared to the standard SLR, the body is widened by 60 mm at the front and rear, giving it a far more planted and aggressive stance. It’s not just for looks, either - the wing struts go straight through to the chassis, making it functional and overengineered in true MSO fashion.
Volcano: The final flame of the SLR HDK
This particular car, nicknamed Volcano, was recently spotted in London, and it's nothing short of breathtaking. It features a deep, glowing orange paint that manages to be both dark and vibrant at the same time - a perfect match for its dramatic bodywork. Carbon fiber is everywhere, from the massive diffuser out back to the blade-like front splitter.
The interior is just as wild. Orange and black Alcantara cover nearly every surface, broken up by carbon fiber and one of the HDK’s most charming details: a multi-tone orange checkered pattern on the seat inserts, door panels, and headliner. It gives off race car vibes while still being playful and stylish.
The car sits on black 15-spoke wheels, far more subtle than the turbine-style wheels found on the standard SLR, but much more fitting for the HDK’s race-ready character.
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Details that matter
The HDK still packs its iconic 5.5-liter supercharged V8, but MSO gave the exhaust system a serious upgrade. The big, heavy silencers are gone, swapped for lighter, less restrictive pipes, and the usual four exhaust tips have been replaced by a single, neatly angled one on each side. The result? A deeper, more aggressive growl, with that signature supercharger whine that SLR fans can’t get enough of
Power climbs modestly to around 660 PS, and while that might not sound huge on paper, the real gain is in response, weight reduction, and character. MSO shaved off unnecessary mass, reworked the suspension with custom KW dampers, and tweaked the aerodynamics - all without turning it into something too hardcore to drive. It’s faster around the McLaren test track than the standard car, but it's still surprisingly usable and, believe it or not, comfortable.
MSO’s artistic touch
Each HDK build is unique, but Volcano isn't even the most outlandish one we've seen. That title likely goes to the shark-themed HDK that premiered last year, inspired by World War II fighter planes, taking cues from RAF aircraft like the Curtiss P-40 Warhawk - the same one known for its iconic shark mouth nose art. That car featured over 1,000 hand-painted rivets and even interior materials sourced from actual WWII aircraft. It’s that level of obsessive attention to detail that separates the HDK from anything else out there.
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From vision to reality
To understand the HDK, it’s worth looking back. The SLR project began as Project 7, created by a team of ex-Formula 1 engineers at McLaren and brought to life using the company’s pioneering carbon fiber knowledge. When the SLR finally launched in 2003, it confused some purists - it wasn’t a lightweight rival to the Carrera GT or Enzo Ferrari, but something else: a front-mid-engine Super GT, built with Formula 1 tech and German muscle.
The SLR's carbon-fiber monocoque, composite crash structure, and full carbon body made it unlike anything else at the time. It was also the first road car with a carbon front crash structure, another F1-inspired innovation. Paired with the brutal AMG V8 and a 5-speed auto (chosen for its torque handling), it was an unusual but captivating mix.
MSO later revisited the SLR platform with various special editions, like the SLR by MSO and the SLR McLaren Edition, tweaking everything from aerodynamics to suspension. But the HDK is the most extreme expression of this passion project. Only 12 exist, all of them already sold, each tailored to its owner’s vision - and Volcano is the very last one.
