Prime Focus Photography - Use direct with your camera. Simple Barlow Projection - Use above with your barlow and camera. Eyepiece Projection - Use your eyepiece in extension tube. Extended Barlow Projection - Use extension tube with your barlow (Extended barlow projection makes a 2x barlow into a 3x or more barlow). Telescope Mount Adapter: It offers 1.25in mounting sizes on telescope side. M42x0.75mm outer thread on one end and standard 1.25" (31.7mm) fitting on the other. The inside of the adapter is fully threaded to minimize reflections. Threaded to accept standard 1.25" eyepiece filters. T-ring (with M42x0.75mm thread): Connect Nikon DSLR / Canon DSLR camera to the 1.25" Extension tube and Telescope Mount Adapter. Extension tube: M42x0.75mm outer and inner thread, one side is to fit T-ring, the other side is to fit Telescope Mount Adapter. Specifications: Material: Aluminum Color: Black Compatible with: Canon EOS EF mount camera (5D, 5D Mark II, 5D Mark III, 20D, 30D, 40D, 50D, 60D, 100D, 350D, 400D, 450D, 500D, 550D, 600D, 650D, 700D, 750D, 760D, 1100D, 1200D, 1D, 1D MkIII, Digital Rebel T4i, T3i, T2i, T1i, Xt, Xti, XSi, XS......). Telescope with standard 1.25 inch Eyepiece Ports. Compatible with: - Nikon F mount DSLR camera (D4 D4s D3x D3s D3 D810 D800 D750 D700 D610 D600 D300S D300 D200 D100 D7200 D7100 D7000 D5500 D5300 D5200 D5100 D5000 D3300 D3200 D3100 D3000 D90 D80 D70 ......). - Telescope with standard 1.25 inch Eyepiece Ports. Package includes: 1 x Telescope Mount Adapter 1 x T-Ring 1 x Extension Tube