The frame is designed to install astigmatic and stigmatic trial spectacle lenses, prisms, prism compensators, as well as filters, diaphragms and other optical elements. To determine the direction of astigmatism and strabismus, the rim is equipped with an angular scale. Rotation of lenses, prisms and other optical elements relative to the scale is made using a lens holder. The change in the center-to-center distance is made separately, while the value is read from the center of the nasal seal in the range from 48 to 80 mm. To improve the accuracy of the selection of glasses and patient comfort frame allows you to change the length of the ear hooks, their inclination, as well as the inclination and position of the height of the nose pad.