Everyone and their brother has tried to make drivetrains faster with larger derailleur pulleys & ceramic bearings, but absoluteBLACK’s new HOLLOWcage may be a truly revolutionary bike upgrade. The name pretty much sums it up, your conventional cage & pulleys get replaced by a lightweight hollow carbon cage with a giant low friction carbon pulley ring that spins on smooth ceramic bearings, and is quieter than ever…

absoluteBLACK carbon-ceramic HOLLOWcage low friction upgrade

Absolute Black carbon-ceramic Hollow Cage low friction upgrade, PVD rainbow

From the birth of the modern derailleur, the two-plate cage sandwiching two spinning pulleys to maintain chain tension has remained virtually unchanged. Ceramic bearings made the derailleurs faster-spinning and plenty of oversized pulley wheel systems have reduced drivetrain friction overall.

But now, absoluteBLACK promises next-gen performance upgrades with their new carbon-ceramic HOLLOWcage system. The single-sided derailleur cage upgrade is said to deliver faster shifting, silent-running, improved aerodynamics, and the smoothest-rolling low-friction ceramic bearings on the market.

absoluteBLACK claims “super silent” operation, shifting “as good as” stock Dura-Ace cages, improved aerodynamics, and “more watt-savings” than any other cage available!

Tech details – What’s new?

Absolute Black carbon-ceramic Hollow Cage low friction upgrade

all images c. absoluteBLACK

Obviously, everything here is new, so let’s look at the details that make it work. The “mono-plate” cage itself is made of “carbon-polymer” material, which sounds like the same high-performance carbon-reinforced composites we’ve seen from stiff shoe soles to Italian derailleur components.

It also gets a dimpled surface à la Zipp for improved aerodynamics. But absoluteBLACK says that a bit of flexibility in the cage is the secret here allowing the upper pulley to be perfectly placed for precise shift actuation while the lower pulley can more accurately twist to align towards the chainring for reduced friction

Absolute Black carbon-ceramic Hollow Cage low friction upgrade, angled details

The custom pulleys are also made of carbon polymer, with the more conventional closed & stiffer 12T upper guide pulley spinning on an oversized ceramic bearing, but still only attached from one side. The wild-looking, open 18T lower pulley is carbon-polymer again, this time spinning between two custom oversized ceramic bearings, held in place by a custom, scalloped lockring.

Absolute Black carbon-ceramic Hollow Cage low friction upgrade, backside inside

absoluteBLACK says their patent-pending “Silent Xring Pulley” system ensures quieter engagement of the chain to the tall teeth of their pulley, improving the already quieter operation of composite pulleys vs. alloy. Compared to stock Dura-Ace pulleys, they say these “reduce the sound level by 12-14dB” for roughly 60% reduction of pulley noise. The secret they say is the rubber Xring element inside the upper pulley that damps the impact of the chain to the guide pulley’s teeth, which they say was “the single biggest contributor to overall drivetrain noise”.

Absolute Black carbon-ceramic Hollow Cage low friction upgrade, Xring silent detail

Those tall teeth are also said to allow lower spring tension than any other cage on the market, without compromising shift precision. That means lower system friction and more watts-saved, still providing excellent shifting thanks to the unique combination of pulley stiffness and tall teeth profiles. In addition, it is the only cage that can dynamically adapt to the variable chainline, minimizing friction at the lower pulley.

absoluteBLACK HOLLOWcage – Pricing, availability & options

Absolute Black carbon-ceramic Hollow Cage low friction upgrade, colors

The new absoluteBLACK carbon-ceramic HOLLOWcage derailleur upgrade has a 71g claimed, and sells for an eye-watering $700 / 600€ / £520. On top of the standard matte black composite of the pulleys & cage, it comes in five different anodized finishes for the lower pulley lockring – black, gold, red, titanium & PVD rainbow.

Absolute Black carbon-ceramic Hollow Cage low friction upgrade< dura-Ace upgrade

The new HOLLOWcage is currently compatible with Shimano Dura-Ace R9100/R9150 & Ultegra R8000/R8050 series rear derailleurs, and with up to 32T cassettes.



  1. Colin on

    I think they look cool and would use one for that reason alone. But not at that price.

    And to claim they save more watts than any other cage without actually saying how many watts they save is stupid.

  2. whatever on

    Just when I think the bike world is about a ridiculous as you can get, along comes this. This is just stupid and with nothing but marketing speak. Looks cool, but not $700 cool for d–n sure. Shiny new Onyx set of hubs are about the same price and have allot more going for them. Allot better ways to spend $700 bike dollars.

  3. angstrom on

    A couple of interesting ideas in there under the bling. If the upper pulley really is a major noise source, and damping helps, cool. I like quiet.

    Allowing the lower pulley to twist to align with the chain might help noise, friction, and chain retention.

    Those are ideas that could be adapted to more affordable components.

  4. Bryin on

    One more overpriced bike part that has a distinctive look that will help you stand out at your group ride. Identify yourself as complete knob that is willing to waste money to look “cool”.

  5. Crash Bandicoot on

    This occupies the space of, looks cool but it’s one of those things that if you’re good enough for the minute watt savings to make a difference in race performance than someone is providing your equipment free of charge. The dentists that buy this are better served spending the $700 at the anti-aging clinic.

    • Collin S on

      Actually its part of their marketing. Absolute black has this one chain lube that makes your chain look like crap right from the bottle with zero miles on it but claims it saves like 5 watts. If it was clean, then it would show they are not using their own kool-aid.

  6. Jon on

    I’m willing to bet that aerodynamics would be improved if that big hollow in the the lower pully was filled in but that would not look as distinctive. Big through holes with sharp edges are not aerodynamic. Just look at aero wheels. A disc is the most aero.

  7. FrankTheTank on

    I used to have a lot of respect for Absolute Black. I do think their oval chainrings are better engineered and better quality than their competitors. But when they release a ridiculous product like this, it really makes me question what kind of company I am doing business with. I think I will look elsewhere in the future.

  8. Hexsense on

    What is more aero between full disc wheelset or shallow hollow wheelset?
    I imagine the same apply to pulley wheels.

    • Jossin on

      Hi you bet sooner or later they will release a HOLLOWcage cap/cover to improve your efficiency and aerodynamics even more but at a biting eye watering price at just $199 for that

  9. Oli on

    Nobody has managed to produce evidence showing a net gain from these things. Indeed the few that tested extensively showed a net loss in watts, due to friction gains being lower than aero losses.

    As they’re providing no evidence of efficacy I’m sure this product is exactly the same.

  10. James on

    Wonder why race cars don’t use massively oversized bearing diameters at every opportunity? Oh wait, its because they are heavy and the ball bearing has to travel much further than it would otherwise on a smaller axle or inner race. It’s okay if I take the scenic route, but my bearings better not be. Marketing is fun.

  11. K-Pop is dangerous to your health on

    Cost a lot? So what. Marginal gains if anything? So what. People only buy them for aesthetics? So what. No matter what you think about these or any other pulley system they will sell out. I would put money on that every time.

  12. Craig on

    I’ve heard some small German composites outfit is selling an upgrade kit for this. It consists of a 16 tooth lower wheel and a shorter cage and its 5 grams lighter. Its 1200 Euro which sounds like fair price too.

  13. alex on

    The important part is missing from this story. How many watts is my $700 saving me? As far as aerodynamics got, the cross section of a derailleur cage is so small that the savings can’t add up to much, if anything.


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