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Absolute Black Hollowcage Carbon Ceramic Oversized Derailleur Pulley Cage



Very expensive, very quiet, very controversial
Reduces drivetrain noise
An instant conversation starter
Only fits Shimano SS derailleurs

At every product is thoroughly tested for as long as it takes to get a proper insight into how well it works. Our reviewers are experienced cyclists that we trust to be objective. While we strive to ensure that opinions expressed are backed up by facts, reviews are by their nature an informed opinion, not a definitive verdict. We don't intentionally try to break anything (except locks) but we do try to look for weak points in any design. The overall score is not just an average of the other scores: it reflects both a product's function and value – with value determined by how a product compares with items of similar spec, quality, and price.

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The Absolute Black Hollowcage Carbon Ceramic Oversized Derailleur Pulley Cage has a price tag about as big as its name. The £519 upgrade is unlikely to make you beat your mates to the café, but neither is it going to slow you down, and when you get there just about everyone is going to want to talk to you about it (from experience). The cage meets its claims to reduce drivetrain noise which on slow climbs does make standard setups sound rather rudimentary, and shifting with it fitted was crisp and precise, but my word that price is quite something.

The Absolute Black Hollowcage has created quite the stir since its release, for reasons both good and bad. For a few days it seemed like every other picture on Instagram was of the unique pulley cage, with most people clearly liking its looks at the very least. Then there's the price, £519, enough dosh to buy a bike with; but people have proven that there's a market for ludicrously expensive oversize pulley wheels (OSPWs), as CeramicSpeed has had no problem in shifting its £379.99 systems – so much so that you're more likely to be unique if you turn up with a standard derailleur cage at the rich boys' café run.

Then there's the accompanying marketing material, which doesn't exactly beat around the bush:

  • It is super silent (over 12dB noise reduction vs stock).
  • The shifting is as good as with the original Dura Ace cage.
  • It's more aero than the OEM cage and other oversized cages.
  • It saves more watts than other cages
  • One of the lightest oversized cages on the market.
  • First mono plate construction of its kind.

These have raised their own questions and a certain Youtube video which you now can't watch in the UK. So, after six weeks with the cage, let's take a look at what I've found.

> Buy this online here

Firstly, I think it looks great. The one we've got is the rainbow PVD colour but there's also red, gold, black and titanium available. It looks different to any other cage on the market and because of that has garnered more attention during rides than just about anything else I've tested.

At the moment the cage is only available for Shimano and is compatible with its 8000 Ultegra and 9100 Dura Ace SS derailleaurs.

Fitting the cage is pretty simple: you will need to remove the chain, use a Torx T10 key to remove the bolt holding in the existing cage, twist and remove that one, and then repeat the process in reverse to fit the Hollowcage. I found the instruction video on the Absolute Black website extremely informative and easy to follow, and I wish more brands would follow suit with similar installation and maintenance help.

Next, you're required to size your chain. This should be similar to the one taken off, and this is where I hit a problem.

In big/big gears the rear mech was at its extremity, with very little chain wrap, and yet in small/small or pretty much any gear in the little ring in fact, the chain was baggy. I was stumped by this for some time, having followed the chain length video to a T. I decided to try the cage in the other two spring tension settings, but to no avail. I finally gave up and emailed customer support, and following some very polite and punctual responses it turns out my 'medium' cage (GS) derailleur was incompatible. On AB's website it is stated that the Hollowcage is 'NOT compatible with Ultegra long GS cage derailleurs.' I'd got caught out by assuming that the medium would be fine... Turns out that on the Shimano website there isn't a long one, so this is going to limit the number of people who can use the Hollowcage quite dramatically.

2021 Absolute Black Hollowcage Carbon Ceramic Oversized Derailleur Pulley Cage - on bike 1.jpg

Anyway, happily I refitted the cage to an SS rear mech and the chain sizing went far more successfully.

Quietly does it

Once on, I spun the pedals, re-indexed my gears and was seriously impressed with just how quiet it was. Pulling out a decibel meter, I measured a reduction of 15dB compared to standard (two-week-old) Dura-Ace jockey wheels, which is not insignificant. Out on the road, this is completely irrelevant when travelling at over about 25kph as wind noise is far more prevalent. However, when travelling slower on climbs, especially on a still day, you can make progress with eerily little noise. I've never really thought of a standard drivetrain as being noisy, but you do generally hear if someone's on your wheel, and swapping between bikes during testing did highlight just how clanky even a 'quiet' drivetrain can sound.

2021 Absolute Black Hollowcage Carbon Ceramic Oversized Derailleur Pulley Cage - 5.jpg

So, the first claim seems absolutely true. Apparently, this is due to the 'xring rubber suspended bands, that dampen the chain impact on the guide pulley teeth'. All I know is I liked sneaking up on riding buddies.

Slick shifting

The second claim is that shifting is as good as when using the original Dura-Ace cage. This is a big one as the top-of-the-range Shimano groupset is famous for its crisp, direct shifting; I believe this could be the main reason we haven't seen the whole pro peloton adopt OSPW systems yet, although some teams such as Astana Premier Tech were using them at Grand Tours this season. After 1,000km with the cage, I must say it impressed; it requires less b-screw than a CeramicSpeed alternative fitted to the same mech, resulting in more accurate and reliable shifting.

2021 Absolute Black Hollowcage Carbon Ceramic Oversized Derailleur Pulley Cage - on bike 4.jpg

Is it as good as Dura-Ace? In a blindfolded test I'm pretty sure I couldn't tell the difference between the two, so I'll give it the benefit of the doubt.

More aero?

Claim number three: It's more aero than the OEM cage and other oversized cages. Hmmm... well, to back this up Absolute Black has published some results and a video on its website, and firstly I'd like to say that if I published a graph like that, I don't think I'd have passed my aerospace degree. However, what it does show is that IF a completely laminar flow hits the cage while it's in THAT particular position, then it outperforms its competition.

> How to get more aero without spending a fortune

Is this comprehensive proof that it's more aero? No, I don't think it is. For a start, your legs are going up and down and around in front of it, meaning the flow of air hitting the cage will be all over the place – technical term there, I know. A wheel is spinning extremely quickly next to it, causing further disruption, and also, as AB's own graph points out, the differences are in the 0.1s of a watt. Now, I am all for a marginal gain, but I am completely of the mindset that this microscopic amount of difference has no meaningful effect on even the quickest of riders, and in an attempt to show that larger cages aren't slower AB has shot itself in the foot, rather. Conclusion – don't buy it because it's more aero, don't not buy it because it's less aero.


Claim number four: It saves more watts than other cages. Well, there are no numbers mentioned but once again we're treated to a graph. This one shows that the 'special grease' is nearly as quick as oiled or dry bearings, coming in with just 0.04W in real-life conditions under load. I assumed this was GraphenLube because that's what it says to top it up with during services, but AB says that it is a proprietary petroleum-based grease. It's impressive, but as AB says itself, 'Bearings, contrary to common assumption, are not the place of big savings (0.03-0.1W between high-quality bearings).' So let's move on.

2021 Absolute Black Hollowcage Carbon Ceramic Oversized Derailleur Pulley Cage - with GraphenLube and box.jpg

They don't spin freely... this is not something I have a problem with – heavy aluminium jockey wheels have far more inertia to keep them spinning, so some light plastic ones are never going to spin for as long. Friction under load and at different chain line angles is far more important, I can agree with AB on that one. So, is that big bearing actually any better? I highly doubt it; in a bigger bearing the balls/races move over each other far faster than in a small bearing, but as it makes a negligible difference when they're spinning so slowly when compared to an industrial machine, who cares? Maybe they are 0.1W slower, maybe they're 0.1W faster, which in my mind can be sacrificed in the name of aesthetics and design.

Sticking with claim number 4 a bit longer, I was under the impression that OSPW systems save watts by reducing the radius that the chain has to go through around the jockeys. In part this is true, but only really significant when the chain is under tension, that's as it enters the chainring and exits the cassette. So larger jockey wheels don't really do anything other than look pretty and maybe facilitate a little less chain tension (which would reduce the friction from the chain a tiny amount).

2021 Absolute Black Hollowcage Carbon Ceramic Oversized Derailleur Pulley Cage - 6.jpg

Having tried the cage in its lowest chain tension setting, I found the chain slapping when in small/small gears offputting and feared dropping a chain. Hence, I opted to use the cage in its medium-chain tension position, solving the chain slap but also most likely negating any tiny watt savings I was getting over a standard cage. Since THAT Youtube foray, I've been sent a video by AB detailing its testing procedure. It certainly looks thorough and as if it should get reliable results. I'm therefore of the opinion that yes, the cage can save more watts than other cages, but when in its lowest chain tension position. On real-life roads I found it impractical to run it in this position, but for smooth TTs you could probably take advantage of it, though actually we're talking about numbers so small that there are far better and far more cost-effective ways of 'buying speed'.

2021 Absolute Black Hollowcage Testing rig.jpg

Low weight

Claim five: One of the lightest oversized cages on the market – we're almost there! The Hollowcage has a claimed weight of 71g and came up as 70g on our scales; that's certainly light, but you're not likely to save a lot, if anything. According to CeramicSpeed its system 'weighs approx. 70g, making the difference between a standard rear derailleur pulley system and the CeramicSpeed OSPW System negligible'.

Unique design

Claim six: First mono plate construction of its kind. At least it's an easy one to finish... YES, I haven't seen any other derailleur cages like it.


As with any oversized pulley wheel system, I don't think you should buy it for aero reasons, weight or a reduction in drivetrain watts. There are loads of better ways to gain speed, however good you are, without spending this much. If, however, you're buying it to personalise your bike, stand out from the crowd or simply because it makes you happy, then rest assured that just about all of us have spent money on needlessly expensive upgrades and this one is bound to garner plenty of interest.

Regardless of whether you believe me, people on Youtube or Absolute Black, I think we can all agree that it's not going to significantly slow you down. In my experience the shifting has been more than adequate, and personally I think it looks bang tidy.


Very expensive, very quiet, very controversial

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Make and model: Absolute Black Hollowcage Carbon Ceramic Oversized Derailleur Pulley Cage

Size tested: 9100/8000

Tell us what the product is for and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?

Absolute Black says: "Our revolutionary mono-plate OSPW design is the quietest, best shifting, aerodynamic derailleur cage design created to date. It is a dawn of new era for rear derailleurs." It's certainly unique, is very quiet, has excellent shifting attributes and the aero claims are fairly insignificant in the grand scheme of things. At £519 it's for riders with money to spend on blinging out their bikes and looking for a conversation starter.

Tell us some more about the technical aspects of the product?

From Absolute Black:

Size (Mass +/-1g):71g

Color: Lower lockring: PVD Rainbow, Black, Titanium, Red, Gold

Compatibility:Shimano Dura Ace 9100 / 9150 / 9170 , Ultegra 8000 / 8050. Fits up to 32T cassette. NOT compatible with Ultegra long GS cage derailleurs..

Materials used: Carbon fiber-polymer matrix, 7075 Aluminium, rubber, ceramics

In the box: Complete cage, lockring tool, 2x spare xring rubbers

Rate the product for quality of construction:
Rate the product for performance:

Shifting performance is good, noise is reduced, and I don't think it's any slower than a standard setup and certainly no less aero.

Rate the product for durability:

No issues after 1,000km. The fully ceramic bearing is an unknown but has a four-year warranty for peace of mind. Maintenance of bearings has been considered and a tool included in the box.

Rate the product for weight (if applicable)

A competitive weight, very similar to a standard Shimano Dura-Ace cage or CeramicSpeed OSPW system.

Rate the product for value:

It's over £100 more than the CeramicSpeed option...

Tell us how the product performed overall when used for its designed purpose

It performed well; shifting performance was a pleasant surprise, drivetrain noise reduction claims were true.

Tell us what you particularly liked about the product

I like its looks and the reduction in drivetrain noise.

Tell us what you particularly disliked about the product

I think it could have been clearer that this would not work with MEDIUM cage derailleurs. The "long" next to the GS on the website is misleading as Shimano does not appear to use this same nomenclature. Not a problem if you have a Dura-Ace mech, as they are all SS.

How does the price compare to that of similar products in the market, including ones recently tested on

It's expensive but OSPWs always seem to be. The CeramicSpeed OSPW is the obvious competitor and that's got an RRP of £379.99.

Did you enjoy using the product? Yes

Would you consider buying the product? No

Would you recommend the product to a friend? A very rich one.

Use this box to explain your overall score

It's hard to score! It worked well, shifting was precise and the drivetrain noise reduction claims were real. However, at that price it doesn't offer any significant performance benefit and hence becomes a bit of a fashion accessory. I personally love that Absolute Black has created something that looks different to anything else on the market without hindering performance.

Overall rating: 6/10

About the tester

Age: 23  Height: 6ft  Weight: 74kg

I usually ride: Specialized venge pro 2019  My best bike is:

I've been riding for: Under 5 years  I ride: Every day  I would class myself as: Expert

I regularly do the following types of riding: road racing, time trialling, cyclo cross, commuting, club rides, sportives, general fitness riding, mtb,

Jamie has been riding bikes since a tender age but really caught the bug for racing and reviewing whilst studying towards a master's in Mechanical engineering at Swansea University. Having graduated, he decided he really quite liked working with bikes and is now a full-time addition to the team. When not writing about tech news or working on the Youtube channel, you can still find him racing local crits trying to cling on to his cat 2 licence...and missing every break going...

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