The Lensbaby Fisheye Optic has an ultra-wide 12mm focal length and 160° field of view that captures eye-popping views from infinity all the way down to 1" from the front of your lens. The Fisheye Optic is designed for use with the Composer, and can also be used with the Muse with the purchase of a special adapter.
Simply pop out your installed optic with the optic swap tool and drop in the Fisheye Optic and presto, your Lensbaby Composer has become a Fisheye lens. It will also work with the Muse and Control Freak with a special adapter. You can change your apertures by unscrewing the front element and switching the aperture disk that rests just above the bottom element.