Orion 05641 Superwide 2" Prime Focus Adapter for Nikon Cameras, Black Super wide Adapter provides widest clear aperture possible for full-frame DSLR Imaging performance without vignetting Integrated Nikon F-mount bayonet 10mm optical length Tapered 2" barrel couples Adapter to 2" telescope Focuser more securely than Typical t-adapters Glare-threaded, flat-black interior ensures excellent contrast