Guardian Forearm Crutches Tall Adult (Pair) Jobst Anti Embolism Stockings Accepted by leading authorities as Jobst Relief 20 30 Knee Hi Accepted by leading authorities as a simple and accurate method for discovering congenital color blindness and red green blindness each in two forms complete and incomplete * Includes four special plates for tests to determine the kind and degree of defect in color vision * Makes use of the peculiarity that in red green blindness blue and yellow appear remarkably bright compared with red and green * Color plates encased in specially designed album type books for ease of handling * Detailed instructions included It allows up to six pairs of data for viewing and recording to greatly speed up data capture and analysis * Heavy wall high strength aluminum tubing * Telescoping parts are manufactured with internal bushings and external lock nuts to provide totally silent usage