SIGMA 17-50mm F2.8 EX DC OS HSM Zoom Lens. Model: 17-50mm F2.8 EX DC OS HSM. Features: Optical Stabilization (OS), Hyper Sonic Motor (HSM). Maximum Aperture: F2.8. A versatile standard zoom lens featuring a constantF2.8 aperture throughout the zoom range andOptical Stabilization (OS) for improved handheld shooting performance.
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