Instruction: Extract information from the supporting document to answer the given question.

Input:
Question: size of gasket?
Document: This is an OEM part for the Bialett Moka Express. It fits the 6 cup size perfectly. In fact, it fits better than the original gasket that came with pot.
Like all good things, time wears our material items thin. So changing the gasket on the Bialetti coffeemaker is important. That way the landfills won't be filled with metal pots because a little rubber ring wore out! I have looked for the gaskets and replacement filter in retail stores to no avail. So I was delighted to find these online. There are many sizes of Bialetti's, so make sure you purchase the right size.
I bought this for a 6 cup Bialetti that is 40 years old. The gasket fits, but it didn't really work, which could be related to the age of my Espresso maker. The old gasket allowed the hot coffee to come out the sides when cooking, and this one was no different. Maybe there is a flaw in my Bialetti, or maybe the gasket should be slightly larger, but theses gaskets appeared to be the same size as the original one that came with the maker.
After melting the gasket due to making coffee without water (yeah you can laugh) I was upset about the loss of my beloved moka pot. When someone told me I could buy a new pot on Amazon I was amazed to see that I could purchase a new gasket as well. My only advice would be to measure, measure, measure. I bought the wrong size from a local store because they only had the one size. At least Amazon had all the parts necessary.
These are great replacements for my Bialatti espresso maker. It's one size fits all- regardless of model # - extremely pleased!
The perfect item to make you Bialetti last a long time. Just make sure you get the right size or it is useless.
Make sure you go on Bialetti's website to check out infor on sizes so that you buy the right size for your pot. Mine fits quite well
I don't trust some of the cheap ones available in local supermarkets. They might not last, have strong smell or not be food-grade quality!If you are not sure about the size, check this out: [...]
Finally ordered the correct gaskets. Initially I got the 3 cup size, but no, they were too small. So I ordered the 6 cup and they fit perfectly. They fit like the original and shipped fast.
Love it, especially since it is an original replacement part from the manufacturer. I was a little worried if the size would be the same, but it was the perfect fit. I had some trouble finding out what size my Moka pot was, but they have wonderful instructions in Bialetti's website to find out the right sized replacement parts.
Answer: 72 mm outside x 55 mm inside for the 6 cup size.