It’s plastic. I have one of these and often have to wait a few minutes before it’s cool enough to drink.
I do like this thing. I like how I can preload my mug with milk and/or sweetener and the action of the tea pouring into the mug mixes it up nice.
I also like that it fits perfectly on my favorite mug and matches the volume so there’s no risk of overflow. But that’s just serendipity.
