Canon EF 25 II Extension Tube for EOS Digital Cameras Retains all metering and AF functions with most CANON EF lenses Exposure compensation is often required with cameras other than the EOS-1 Series. High level water and dust resistance -- suitable for use in heavy rain Retains all metering and AF functions with most CANON EF lenses O-ring seals protect mounts and release lever Retains all metering and AF functions with most CANON EF lenses High level water and dust resistance -- suitable for use in heavy rain O-ring seals protect mounts and release lever