an adjustable winged eyecup allows the user to apply it to many makes and models of existing and new optics . the winged eye cup is essential for eliminating light and elements while using an optical device such as a binocular or monocular . the winged eyecup can also provide a constant eye relief for the optical device . it is designed to be removable and the same winged eyecup can be applied to many different makes and models of optical devices .