The Sigma 2x Teleconverter EX APO DG for Canon is a third-party teleconverter for use with compatible telephoto lenses. Key features include:

2.0x Conversion. The Sigma 2x Teleconverter EX APO DG doubles focal length while only reducing the maximum aperture by two stops.

High-Quality Optics. The apochromatic six-element/five-group lens design has a multi-layer coating that cuts down on ghosting and flare.

Retains Lens Functions. This teleconverter retains communication between the lens and camera, meaning that you can still use autofocus and automatic metering.