Simple Barlow Projection Use with your Barlow lens and camera. Eyepiece Projection Use your eyepiece in an extension tube. Extended Barlow Projection Use extension tube with your Barlow (extends magnification; a 2x Barlow can become 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) fitting on the other. Fully threaded interior to minimize 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 side connects to T-ring, the other to the telescope mount adapter. Specifications: Material: Aluminum Color: Black Compatible with: - Canon EOS EF mount cameras (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 (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