The Tamron 70-300mm Sony FE Mount Lens F4.5-6.3 Di III RXD is the first model designed for full-frame mirrorless cameras Tamron has adopted a dedicated design for mirrorless cameras and achieved a compact size once again by fixing the aperture at F/6.3 at the telephoto end. The maximum diameter is 77mm. Measuring just 148mm and weighing a mere545g, this 70-300mm F/4.5-6.3 Di III RXD is the world’s smallest and lightest telephoto zoom lens for full-frame mirrorless cameras. Compatible with Sony’s popular E-mount cameras, it has been developed with the concept ofenabling photographers to more easily experience the universe of full-scale, full-frame 300mm telephoto photography. Superior optical performanceand supreme lightweight portability Pursuing lightweight design as a top priority, Tamron has created a compact 70-300mm Sony Lens that makes 300mm telephoto shooting easy and fun. The superb optical design is based on a rigorous simulation processusing state-of-the-art design technologies. As a result, Tamron has successfully struck a balance between extreme lightness (545g) and compactness, incorporating a slim lens barrelwith a maximum diameter of 77mm without sacrificing high image quality. The optical design includes15 elements in 10 groups, with an LD (Low Dispersion) lens element precisely arranged to suppress axial chromatic and other aberrations that are likely to happen with telephoto zoom lenses. Moisture-Resistant Construction for added protection Seals are located at the lens mount area and other critical locations to deter infiltration of moisture and/or rain drops and afford Moisture-Resistant Construction. This feature provides an additional layer of protection when shooting outdoors under adverse weather conditions.