This is a glass piece to be used with a Lensbaby Composer Pro or Composer Pro II. Use it to create beautiful swirling bokeh in the backgrounds of your images. You should look up some example images with this attachment, I think that you'll be impressed.
This one is in excellent condition with little wear. The glass is clean and scratch-free with no haze, fungus or other problems. It comes with the front cap and the bubble.