Unlike extension tubes which have no glass, close-up lenses are essentially a sophisticated magnifying glass which you screw onto the filter mount on the front of your Canon lens to enlarge your subject. This set from SRB is made in the UK and includes four close-up lenses of different dioptres, offering varying magnification strengths. They can be used individually or stacked together to multiply the effect. These are particularly useful when using longer focal lengths because the magnification needed is less, so the image suffers less degradation at close distances.
This set includes +1, +2, +4 and +10 dioptres in a fold-up case. The lenses are single element. Choose the right set for your lens filter size. They can also be used with stepping rings so buy for your largest filter mount and step down for lenses with smaller filter mount sizes.