The ring that stops the brew water from taking the wrong path
The seal between the shower screen and the group body has to be tight, otherwise the water finds its way past the shower screen instead of through the coffee grounds. This O-ring does exactly that job – and because it constantly alternates between 90 degrees hot and cool, it is a classic wear part. Part number R499905544.
According to the documentation, the same number is also used at the group connection of the R9. An old O-ring is hard, shows a permanent imprint and no longer springs back when you squeeze it between your fingers. By then at the latest, it only seals as long as you tighten it hard – and that comes at the expense of the thread.
When it is due
Replacement is due if water escapes at the edge of the shower screen, if the ring has become hard, brittle or cracked, if its cross-section is permanently flattened, and whenever the shower screen is removed anyway. As a rule, an O-ring is never fitted twice – it costs too little for that to be worthwhile.
At a glance
| Type |
O-ring, gasket |
| Installation location |
Between the shower screen and the group body; according to the documentation also at the group connection of the R9 |
| Fits |
Rocket Boxer and R9 |
| Scope of delivery |
One O-ring according to the manufacturer's specification for number R499905544 |
| Part number |
R499905544 |
| Version |
Inner diameter, cross-section thickness and material are not specified in the documentation |
| Brand |
Rocket |
| Installation |
Installation by a specialist recommended |
Important for installation
The ring sits in the pressurised, hot water path of the brew group. Before touching anything, unplug the machine and let it cool down. When fitting it, make sure the ring lies completely in its groove and does not get pinched – a squashed O-ring seals on the first extraction and no longer on the second. We deliberately do not provide step-by-step instructions here.
Who it is for
For anyone removing the shower screen on a Boxer or an R9. If you have the group open anyway, it is best to replace the shower screen, screw and O-ring in one go. For businesses, a small stock is worthwhile – the ring costs next to nothing and would otherwise hold up an entire service appointment.
What goes with it
From our workshop in Bern and Zurich
We never fit new O-rings dry; instead, we moisten them with a few drops of water first. Rings fitted dry twist when tightened and then sit crooked in the groove – with water, they slide into place. This is our routine, not a manufacturer requirement. We like to do the test extraction afterwards with Nutty Delight or Cozy Chocolate, and in hospitality settings with Very Nutty. More in our coffee bean selection.
Returns excluded
Original spare parts are excluded from exchange and return. They are procured to order and cannot be resold after installation or a test fitting on the machine. So before ordering, please check the model, year of manufacture and serial number of your machine – or drop us a line and we will clarify the fit together. Your rights in the case of defective goods remain unaffected.
What are the dimensions of the O-ring?
Inner diameter, cross-section thickness and material are not specified in the documentation. For O-rings, the part number is therefore decisive: R499905544.
Can I use an O-ring from an assortment box?
We advise against it. In brew water at around 90 degrees, the material is crucial, and a standard NBR ring will not last long there.
Is the shower screen included?
No. We list the shower screen and retaining screw as separate items.
Is it true that the same ring is also used at the R9 group connection?
That is what the documentation for number R499905544 says. If you need the part for that position on the R9, send us the serial number to be on the safe side.
Can I see the part in your showroom?
Yes. We are in Bern at Gerberngasse 44 and in Zurich at Hagenholzstrasse 50b.
Unsure about the fit? Send us your machine's serial number at [email protected]. We deliver across Switzerland and to Liechtenstein in 2-4 working days.
