Sigma 24-135mm f/2.8-4.5 IF Autofocus Lens for Canon SLR Cameras Lens features one Special Low Dispersion ( SLD ) glass element, and two Aspherical elements, resulting in excellent correction of chromatic aberration Inner focusing system features non-rotating front lens barrel for simplified use of filters Custom designed hood with bayonet mount included to prevent extraneous light from degrading image quality All materials used in this lens are lead and arsenic free Filter Size - 77mm