The hard heart of the brew group, for when your shots become unsettled
Inside the brew group, a piston runs in a cylinder, and this cylinder is made of ceramic. Ceramic is used because it is very hard, very smooth and completely indifferent to hot water – exactly what you need in a place where something constantly slides back and forth at almost a hundred degrees. This repair kit has the part number R299906767.
Wear shows up in the shot, not in the part. The lever runs rough or unevenly, the pressure no longer holds steadily, the shot collapses, or water leaks out somewhere it never did before. Open the group at that point and you will find a cylinder with scoring or a dull, roughened running surface. Resealing no longer helps in this state – the new seal wears in on the rough surface straight away.
When it's due
- Your shots have become unsettled and the pressure fluctuates.
- The lever or piston runs rough, sticky or unevenly.
- Water escapes from the group even though the seals are new.
- The seals only last a short time before they wear in again.
- The cylinder shows visible scoring, limescale crusts or a dull running surface.
At a glance
| Type |
Ceramic cylinder, repair kit |
| Location |
Inside the brew group |
| Fits |
Rocket espresso machines – the documentation does not name a specific model series |
| Scope of delivery |
The scope follows the manufacturer's specification for number R299906767. The complete brew group is not included. |
| Part number |
R299906767 |
| Version |
As a repair kit. Dimensions are not given in the documentation. |
| Installation |
Fitting by a professional is recommended |
| Brand |
Rocket Espresso |
Who it's for
For workshops and experienced home mechanics who overhaul a brew group rather than replacing it entirely. If you only need a new seal, this isn't the right part; but if you're resealing for the second time and it still won't hold, this is usually exactly your problem.
Important for installation
The cylinder sits inside the brew group, in a pressurised and very hot area. Before any work, the machine must be switched off, unplugged, completely cooled down and depressurised. We deliberately don't give step-by-step instructions here – dismantling a brew group takes experience and the right tools. Ceramic is hard but brittle: it can't take a knock or being used for leverage.
What goes with it
From our workshop in Bern and Zürich
We run a fingernail across the running surface before we decide. If it catches, the cylinder is due; if everything feels smooth, a seal kit is enough. This one simple check has already saved us many unnecessary orders. That's our routine, not a manufacturer requirement. Once the group is back together, we pull three espressos in a row as a final check – ideally with Nutty Delight or Cozy Chocolate, or something stronger with Very Nutty. More under coffee beans.
Returns excluded
Spare parts are excluded from exchange and return. They are sourced specifically for each order and cannot be resold once they have been fitted or test-fitted on a machine. So before ordering, check the model, year of manufacture and serial number of your machine – or drop us a quick message and we'll clarify the fit together. Your rights in the case of defective goods remain unaffected.
Frequently asked questions
What is the difference from number RA99905814?
They are two different items with clearly different numbers. This one is listed as a repair kit, the other as a complete ceramic cylinder including metal screw. The exploded view tells you which one belongs to your machine – or we do, if you send us the serial number.
What exactly is included?
The scope follows the manufacturer's specification for number R299906767. The documentation doesn't break it down, and we won't claim anything. What is definitely not included is the complete brew group.
Is this an electrical part?
No. The ceramic cylinder is a purely mechanical component in the brew group with no electrical function whatsoever.
Isn't a new seal kit enough?
If the running surface is still smooth, yes. If the cylinder is scored or dull, every new seal will wear in again straight away – then the cylinder is the right way to go.
Can I look at the part in your showroom?
Yes, gladly. You'll find us in Bern at Gerberngasse 44 and in Zürich at Hagenholzstrasse 50b. Bring the serial number or the old part with you.
Questions about the fit? Write to us at [email protected]. We deliver across Switzerland and to Liechtenstein in 2-4 working days.
