The heart of the Adap-T system is the eyepiece adaptor ring "A", which fits quickly and easily around the recess exposed by removing the rubber eyecup fitted to most popular 31.7mm eyepieces. Three grub screws achieve a precision fit using the supplied hex key. Please note that an additional T-threaded camera adaptor ring "B" is required to attach a digital or SLR camera. Many digital camera will also require a proprietary camera lens adapter. Some examples are: Olympus C8080/C7070/C770/SP310/SP350 Nikon 5400/5700/8700/8800 Canon A510/A520/A610/A620/S2 IS/Pro 1 Fuji 6900/S602/S7000/9500/S5000/S5500/S5600