I visited Petrozavodsk in Russian Karelia last week, and was served green tea in a pot like this at a restaurant. I thought it was brilliant, and asked the waitress (via Google Translate) where I might buy one. She had no idea, but I eventually found one in a tiny tea shop, in a basement, through two dress shops. Yay! It works a bit like a gravity strainer: the tea steeps in the large internal compartment (plastic) and when it’s done, you press the button, and the tea is rinsed down into the pot itself (glass). It’s very nice for teas that can be steeped more than once, such as oolongs. So far it’s worked fine, though it can be a bit hard to clean all the leaves out. I’m not sure how sturdy the plastic parts are – I’ll have to use it for a bit longer to find out.