Moen Dual Tub Grip Locking Support Grab Bar Opthalmoscopes Heads Calorie and Distance 14283 Calorie and Distance 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 The Dual Tub Grip has an integrated adjustable locking mechanism that attaches easily to most bathtub walls from 3 to 5 1 4 thick * Simple clamp means no difficult twisting motion during installation * Two textured grab areas at different heights for maximum security and flexibility when entering or exiting the tub * No tools required * Tested to withstand up to 350 lbs