Simple Barlow Projection - Use with your Barlow lens and camera. Eyepiece Projection - Use your eyepiece in an extension tube. Extended Barlow Projection - Use an extension tube with your Barlow lens (extends magnification, turning a 2x Barlow into 3x or more). Telescope Mount Adapter: Features 1.25-inch mounting size on the telescope side. M42x0.75mm outer thread on one end and standard 1.25" (31.7mm) barrel on the other. Fully threaded interior to minimize internal reflections. Threaded to accept standard 1.25" eyepiece filters. T-Ring (with M42x0.75mm thread): Connects Nikon DSLR or Canon DSLR cameras to the 1.25" extension tube and telescope mount adapter. Extension Tube: M42x0.75mm outer and inner threading. One end connects to the T-ring, the other to the telescope mount adapter. Specifications: Material: Aluminum Color: Black Compatible with: Canon EOS EF mount cameras including 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. Nikon F mount DSLR cameras including 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. Telescopes with standard 1.25-inch eyepiece ports. Package includes: 1 x Telescope Mount Adapter 1 x T-Ring 1 x Extension Tube