Unopened. I bought two of these about four years ago, and opened one, but it didn't seem to suit my bird, so I'm selling the remaining one. It's about 10cm long, and a wooden washer is included, so it can be attached to a cage. 〈Reference Information〉 I think it's probably the same as this: https://www.yodobashi.com/community/product/100000001008719913/review.html Thank you for looking.