Buy from Amazon.com : http://fave.co/1FzXrdi
Samyang SY300M-M-BK 300mm F6.3 Mirror Lens for Canon M Mirrorless Interchangeable Lens Camera
Product Description :
300mm Mirror Lens with F63 Aperture
Constructed of 9 elements in 9 groups
Designed for mirrorless interchangeable lens cameras
Minimum focusing distance 295 feet angle of view 54 degrees on Canon M Fuji X and Sony NEX 42 degrees for MFT