The Entaniya Hal 250° Lens E-Mount 3.6mm Kit from B&H combines all three components that make up the Hal 250° Extreme Fisheye Lens. It includes the Front Group Element (which is the optical factor of the lens), the Rear Group Element (which determines the focal length), and a Camera-Mount Adapter.
The E-Mount Adapter attaches to the Rear Group element and achieves a 3.6mm focal length. Other mount types and focal lengths are available sold separately. The Hal 250° lens is offered in three different parts to provide you with the flexibility to simply swap parts instead of purchasing multiple lenses.