Sigma 17-50mm f/2.8 EX DC OS HSM Zoom Lens for Canon DSLRs with APS-C Sensors For Canon DSLRs with APS-C Size Sensors - Multi-Layered Lens Coating 4 Stops of Anti-Shake (OS) Compensation - Excellent Correction for Aberrations Aperture of f/2.8 throughout Zoom Range - Hyper-Sonic Motor for Quiet/Fast AF Accepts 77mm Filters - Close Focusing Distance of 11" (28cm) Ultra Compact (Only 3.6", 91.8mm Long) - Weighs Only 19.9 oz (565 g)