But because the birds would often peck it off, they later changed to silver bands. After constant improvements, what is used today is a rustproof band made of incoloy.
但因線圈常被鳥啄掉，後來改用銀環，此後更不斷改進，今天使用的已是可經長年不朽的鎳、鉻合金制腳環。