Its not that sharp, its a tube of brushed aluminium around, around 2cm in diameter, the walls ca. 1 mm thick. It's tapered at the top (which can be seen in the image). I put tea in there and coudldn't get it out after it had swollen in the hot water. I opened the bottom, put the handle of a wooden cooking spoon in, hold the cooking spoon with both hands and pushed the tea tube against a wall. The tea suddenly gave loose, and the tea tube shot down the cooking spoon to where my hand was holding it. It only hurt after the shock of seeing a groove in my fingertip was over, and it seemed like and eternity until there was blood (but then lots of it).