Auto Focus Macro Extension Tube Set for Nikon SLR Cameras Metal Bayonet It includes 12mm, 20mm &amp; 36mm tubes. The Pro Series auto-focus macro extension tube set is specifically designed for Nikon DSLR and SLR cameras: It includes 3 tubes which can be used individually, or in combination to achieve the desired magnification. Perfect for flowers, insects, coins, stamps, and any close-up shots you want to take