La Pavoni Europiccola Tank to Base Gasket
If you put this gasket between the tank and the top of the base you may get a leaking problem. It seems it is thicker than the old part it replaces and, in my case, would not allow the bottom o-ring to seal. Took a long time an a lot of leaking to figure out this problem. I removed this gasket altogether and, voila, problem solved.