20.50 by 3.20 – the ring you don't have to guess
Most O-rings in an espresso machine come without any dimensions, and you order them by part number and hope for the best. This one is different: inner diameter 20.50 millimetres, cross-section 3.20 millimetres. You can measure the ring you've removed and be sure before you order.
It sits on the bell, lower position. Like all O-rings, it doesn't wear out visibly but gradually: it gets a few tenths flatter and a touch harder, and at some point the spot that stayed dry for years turns damp.
When it's due
Whenever the joint has been opened – a compressed O-ring doesn't regain its shape. Also when the spot becomes damp or limescale edges form, and when the removed ring is hard, brittle, cracked or flattened.
At a glance
| Type |
O-ring |
| Dimensions |
Inner diameter 20.50 mm, cross-section 3.20 mm |
| Colour |
red |
| Installation position |
Bell, lower position |
| Fits |
The model series are not listed in the documentation for number C469900422. Send us your machine's serial number and we'll check the fit. |
| What's included |
one O-ring |
| Part number |
C469900422 |
| Version |
Original Rocket spare part |
| Installation |
Installation by a professional recommended |
| Brand |
Rocket Espresso |
Important for installation
The ring sits in the water-carrying part of the machine. Before any work, the machine must be disconnected from the mains, depressurised and cooled down. We deliberately don't give step-by-step instructions here – a ring that gets twisted or pinched during fitting won't seal from the start.
Who it's for
For service workshops and for anyone who has measured their old ring and is looking for a part where the dimensions are actually stated.
What goes with it
The counterpart is the red O-ring for the upper bell. We also carry the O-ring for the foot, the O-ring for the steam valve and water tap and the copper sealing ring for the heat exchanger. Everything else under Rocket accessories and spare parts and Service parts.
Workshop tip from Bern and Zurich
We measure every O-ring we remove and note the size on the work order before throwing it away. A used ring is flatter than when new – if you order by the measured value instead of the number, you order too small. That's our workshop routine, not a manufacturer specification. For dialling in after a service we use Nutty Delight, for chocolatey notes Cozy Chocolate and for body Very Nutty. All roasts under Coffee beans.
No returns
Spare parts are excluded from exchange and return. They are sourced specifically for each order and cannot be resold after being installed 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 line and we'll clarify the fit together. Your rights in the event of defective goods remain unaffected.
Frequently asked questions
What exactly are the ring's dimensions?
Inner diameter 20.50 mm, cross-section 3.20 mm. That's what the documentation for number C469900422 states.
What material is it made of?
The material is not documented. The colour is red – the documentation says nothing more.
How do I know which of the two bell rings I need?
By the position: C469900422 sits at the bottom, C449900702 at the top. If you're unsure, send us a photo of the removed rings.
My old ring measures less – do I have the wrong one?
Probably not. A used O-ring is flattened and therefore measures less than when new. Order by the part number, not by the measured old part.
Can I see the part in the showroom?
Yes, you can see it in person in Bern at Gerberngasse 44 and in Zurich at Hagenholzstrasse 50b.
Questions? Write to [email protected]. Delivery across Switzerland and to Liechtenstein in 2-4 working days.
