The Vivitar Macro Manual Extension Tube Set contains 3 different extension tubes for macro 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 set contains 3 different tube lengths; 7mm, 14mm and 28mm, which can be used individually or in any combination to obtain the magnification desired. PLEASE NOTE: These are manual tubes and do not communicate electronic functions, such as autofocus or auto exposure control, between your camera body and mounted lens. Both manual focusing and manual exposure control must be used.