The seals are made from heatproof silicone and are of a standard size, making them a universal fit for all brands. And these are the replacement parts that need to be replaced periodically.
It’s difficult to know the size of the stovetop espresso maker you have unless it is clearly labelled. Also because the “cup” measurement that is given to these stovetop espresso makers is not a common one. The cups are sized for European espresso cups, not North American coffee cups. To know the correct size for your espresso maker, check the diameter (outer width from one side of the circular seal to another) of the gasket you have. So you’re wondering “What size of gasket do I need for my espresso maker?” Then match it up to the sizing below: