The Walters Low Vision 16.5 Diopter Reading Cap Lens for 8x50 and 20x50 Walters monoculars shortens the focal distance to help you perform near distance tasks. This reading cap lens is sold separately from Walters Low Vision monoculars, which feature the highest quality optics designed to produce clear images with minimal distortion. Walters monoculars also feature close focus capability and several Walters Low Vision accessories are available to provide customization that fits your needs.