The details
- Gaggia has kept the same group gasket fitting across the Classic family for decades, and parts sellers list one gasket covering Classic, Classic Pro, and Classic Evo Pro, along with several other Gaggia home machines.
- The standard thickness sold as the OEM replacement is 8.5mm. Listed diameters vary slightly between makers, so do not shop by measurements: buying by machine name is reliable here.
- Silicone versions are widely available and are the owner-community favorite. Rubber gaskets bake hard against the hot group over time and become difficult to chip out. Silicone stays flexible, seals consistently, and comes out easily at the next change.
- An 8mm gasket also fits the same groove. The thinner gasket lets the portafilter rotate slightly further before it seats, which some owners prefer when a new 8.5mm gasket makes lock-in feel too tight.
- Some tune-up kits pair the gasket with a new shower screen and screen holder, which makes sense to replace at the same time.
Choosing between 8.5mm and 8mm
Both thicknesses seal correctly on the Evo Pro. The difference is purely the portafilter's final handle position. A fresh 8.5mm gasket typically locks in with the handle short of center, loosening toward center as the gasket beds in. An 8mm gasket starts closer to center immediately. If your current gasket is original and you do not know its thickness, start with 8.5mm, the commonly listed OEM replacement thickness, but note that gasket thickness has varied by production year: when you pull the old gasket, compare it against the new one before final judgment. There is no performance difference in the cup.
What owners actually do
The standard owner move on a new or newly serviced Evo Pro is to fit a silicone gasket at the first sign of leaking around the portafilter, or preemptively during a first deep clean, especially if the machine shipped with a rubber one. Silicone gaskets on this machine are considered a fit-and-forget part. Owners also flip or replace the gasket rather than over-tightening the portafilter to compensate for a hardened seal, since cranking the handle past center accelerates wear on the basket rim and the group.
How to know yours needs replacing
Three signs: water or coffee spraying or weeping from the rim of the portafilter during a shot, the handle rotating well past center to get a seal, or visible cracking and hardness when you pop the old gasket out. Removal is a screwdriver-and-pick job after taking out the shower screen. If the old rubber has hardened, it may come out in chips: this is normal and a big part of why replacements are silicone.