【The Difference Between MCO-N-PA & MCO-N-A & MCO-N-B 】: The material of N-PA is Metal bayonet + Engineering plastics material ); And the material of MCO-N-A is Metal Bayonet and Body Plastic (the bayonets on both sides of the tube rings connecting the camera and the lens are made of metal) ; The material of MCO-N-B is that only the bayonet where the lens is connected is made of metal, and the rest are made of plastic. | 2. 【Macro /Magnification Function】 Pay less Transform common lens into macro lens to capture the high quality images of small objects, Give a higher magnification at a closer distance, enter the macro world, easy to Take Subtle Pictures. | 3.【Compatibility】 Work with Nikon AF AF-S DX FX SLR Cameras, including D5300, D5000, D3000, D3200, D5100, D5200, D3100, D7000, D7100, D4, D800, D800E, D600, D610, D40, D40x, D50, D60, D70, D80, D90, D100, D200, D300, D3, D3S, D700 | 4.【Flexibility】Tube Lengths: (1) 12mm.(2) 20mm.(3)36mm, use alone or combinations. Note! The focal length of lens should be greater than the length of the tube,to achieve your desired focusing result . | 5.【Auto Focus & Exposure compensation】Note: it needs appropriate ocusing distance(1-3cm) space to Auto Focus function. When use 3 tubes together, there is a little difficult to auto focus. Suggest use manual focus or Increase the lens focal lengths to avoid blurry. & Use all shooting modes of the camera, exposure compensation is required. recommend use the manual mode to change the shutter speed directly to control the exposure level.