Extension tubes a great way to focus much closer to small subjects such as an insect or flowers without the expense and weight of buying and carrying a macro lens. One extension tube takes up only as much room as a couple filters in a camera bag. Keep one or more in your camera bag at all times and you will always be ready for that macro shot.
The Kenko AF Extension Tube Set for Canon RF comes with 2 tubes; a 10mm and 16mm which can be used separately or combined for increased close focus capabilities with longer focal length lenses.
They are designed to enable a lens to focus closer than its normal set minimum focusing distance. Getting closer has the effect of magnifying your subject (making it appear larger in the viewfinder and in your pictures). Extension tubes are exceptionally useful for macro photography, enabling you to instantly convert almost any lens into a macro-like lens at a fraction of the cost while maintaining the lens' original optical quality.
The DG extension tubes have no optics. They are mounted in between the camera body and lens to create more distance between the lens and the sensor or film plane. Moving the lens father away from the camera's sensor forces it to focus much closer than normal. The greater the length of the extension tube, the closer the lens can focus.