Kenko teleplus pro 300 dgx converters are made with precision quality multi coated optical glass supplied by hoya corporation the worlds largest manufacturer of optical glass these glass elements were designed to match the optical quality of the prime lens even at the edges and telephoto zoom lenses the optical design of the elements and light path is wide enough not to cause vignetting the pro 300 family are designed specifically to be used with prime telephoto lenses of 100mm or above