This is Equisetum hymale. It's not a bamboo, but an ancient type of plant considered a "fern ally" since it has no flowers and reproduces sexually by spores. I heard somewhere there used to be giant ones that covered the planet and were the precursors to our fossil fuel.
Cool plant though. We display the regular sized ones in octagon pots in Summer generally for the "cooling" feeling as the main item in the tokonoma. The dwarf variety works well for display with bonsai.