In private correspondence with a few people, the
issue of bottomless portafilters came up. They had bought one (specifically
listed as for their machine, not marked as a generic product) from an on
line retailer. These wouldn't fit E61 type machines(58mm portafilter)
without having the existing 8.5mm gasket changed for an 8mm gasket (which was
not supplied). See forum Topic
If you are buying a 58mm bottmeless (naked) portafilter, ask the vendor if it
will fit on your E61 group machine without a gasket change. If they say "no", or
"I don't know", move on and get one that fits, unless you fancy changing your
gasket of course. If it says on the website that it fits your machine....then it
should, without a gasket change (but still ask the question). E61 machines I
know of, that now come with 8.5 mm gaskets in the UK are: All Isomacs with 58mm
groups (except Venus), Izzo Alex & Vivi, Quickmill
Andreja, Expobar....Pulser, leva, Brewtus II, Office control Machines. To
be honest quite a few machines.
Also remember although the retailer may take it back....it's unlikely they
will want to refund your postage!