The Macro Extension Tube Set contains three different extension tubes for digital SLR or film cameras. They are useful for macro, medical or technical applications. Extension tubes are designed to enable your lens to focus closer than its normal minimum focusing distance, making the subject appear larger in your pictures. The extension tubes have no optics, and convert almost any lens into a macro, saving you the expense of purchasing individual lenses. The Macro Extension Tube Set contains three tubes of different lengths, a 12 mm, 20 mm, and 36 mm, which can be used individually or in any combination to obtain the magnification desired. These extension tubes are designed with all the circuitry and mechanical coupling to maintain auto focus and TTL auto exposure.