1. Macro extension tube set includes 3 tubes of different lengths: 13mm 21mm and 31mm. Use them individually or in combinations. 2. These extension tube can compatible with TTL AE and AF AF mode can compatible with Canon Minolta AF and Canon AF function also can compatible with Minolta Xi series lens to realize electric zoom. 3.Macro extension tube is mounted in between the camera body and lens close-up principle is the same with bellows . The 35mm lens camera can compatible with extension tube 7mm 14mm and 25mm they can be used individually or in any combination to obtain the desired magnification. 4.The same disadvantages of extension tubes and bellows: focusing process is difficult as for the short scenery distance; The flux of the lens will be affected. 5. For example: lens focal length 50mm focus distance to infinity - 0.6mm. The scene within 0.6 M can't shoot According to the different combination of three connecting link and can realize different magnification. Take the F=50mm for example close-up connect ring combination than as the adjusting range (approximate) 1:0.20~1:0.34 1 1:0.34~1:0.48 2 1:0.48~1:0.62 1+2 1:0.62~1:0.76 3 1:0.76~1:0.90 1+3 1:0.90~1:1.04 2+3 1:1.04~1:1.18 1+2+3 1:1.18~1:1.32.