Hollowcage® V2 Shimano 9250 Carbon Ceramic Oversized derailleur pulley cage

Do you find it disruptive when cycling through serene landscapes, only to be distracted by the sound of your bike’s chain engaging with the pulleys? That familiar clunking has been a constant companion for decades, but it’s time for a new era.

Traditional polymer pulleys have long been known for their noise, with aluminium options faring even worse, amplifying sound further. We are proud to introduce a groundbreaking new generation of pulleys, designed to reduce noise by an impressive 5-7dB compared to standard Dura-Ace pulleys—equivalent to a remarkable 40% reduction. In practical terms, this means a far quieter ride.

Our patented solution incorporates innovative X-ring rubber suspended bands, which absorb the chain's impact on the guide pulley teeth, effectively eliminating engagement noise—the primary source of drivetrain sound. From now on, your ride will be quieter than ever, allowing you to experience the subtle sounds of your surroundings like never before.

Our full ceramic bearings have been rigorously tested and independently certified using X-ray diffraction by Lucideon Ltd, a UKAS-accredited authority in ceramics and material science. Technically speaking, our bearings consist of both inner and outer races, as well as balls, all crafted from premium ceramic materials, with polymer seals and cages to ensure optimal performance. In contrast, other common types include steel and hybrid bearings. Hybrid bearings, often mislabeled as "ceramic," feature only ceramic balls, while the races remain steel. True full ceramic bearings, like ours, are entirely ceramic—both the balls and races. We use Zirconia Oxide ceramic for the races and Silicon Nitride ceramic for the balls, complemented by low-friction polymer cages and seals for enhanced durability and efficiency.

The mono plate is made using advanced injection moulding technology which is widely used in the bicycle industry. It allows the manufacturing of very complicated shapes where carbon fibres are optimally aligned during the processing from the pellet to the finished component.

That same type of material and manufacturing process (injection moulding) is used by Sram to make their Red derailleur cage, by Shimano to make Dura-Ace derailleur cage, by CeramicSpeed to make their cages, it is also utilized in Shimano Dura-Ace break levers, mtb rocker links for suspension, tubeless valves, saddle shells and even by Magura to make master brake cylinders (Magura carbotecture). Not to mention that this technology has a very extensive use in automotive industry.

Please refer to the video instruction below. For Sub Compact (<34/50t) and Compact (34/50t) chainring combinations, you can use the lowest spring tension setting (First hole from left). However, If you ride on roads with potholes, cobbles, etc. it is recommended to set the HOLLOWcage to the high spring tension (First hole from right). If you have 52t chainring or bigger, use high spring tension setting.
For service / maintenance instructions please refer to our FAQ page.

In the video below you will also find how to determine the correct chain length for your HOLLOWcage. Following this tutorial is crucial for the proper functioning of the drivetrain.

We offer 4 year warranty on bearings* (for more information please refer to our FAQ page)