“It’s rubber/silicone, the size of a fingertip, doesn’t erase, and about as hard as a bouncy ball but doesn’t bounce like a bouncy ball. It doesn’t light up.”
Answer: “Looks like an ’80s light bulb eraser without the metal bottom; they never really erased anything. Here are a couple of similar ones.”
#17 it's also very practical because the tea dripping from the teabeg spills everywhere when you tilt the cup while drinking.