Tokina AT-X 235 AF Pro AF 20-35mm f/2.8 Zoom Lens F/R Aspherical: Specially shaped front and rear glass elements for better pictures PRO: Tokina's designation for its lenses with its brilliant AF-MF focus clutch Optics are 15 elements in 11 groups, this item for SONY ALPHA/MINOLTA Internal focus: nothing moves externally as focused. The front group moves in and out inside the barrel as zoomed Front and rear elements are aspherical and multicoated