Bialetti Replacement Rubber Seal 1 or 2 Cup Venus Musa St Steel Coffee Espresso Maker bialetti replacement rubber seal/ring/gasket suitable for 1 or 2 cup venus musa mia and kitty stainless steel espresso makers. loose packed. outer diameter 5.4cm - inner diameter 4.2cm. cup size is based on espresso cup sizes and not on regular tea or coffee cup sizes.