This is a cooling part for a moka pot. Used a few times. This part is installed between the body and the tank, and it lowers the temperature of the hot water rising before it hits the coffee grounds. The details are unknown, but I found a moka pot sold with this part attached, so I've included images (Images 13~). It's for a 2-cup moka pot, but it varies depending on the manufacturer, so it can be used if the screw threads match. I've measured the screw thread part. I don't know which manufacturer or model it fits. It fit perfectly on a Cofika moka pot.