RECOMMENDED: Made by Essilor, the world's leader in eyeglass lenses. Crystal Vision polycarbonate bifocal lenses for reading and distance vision viewing means that the reading area has a half moon shape with a "flat top", in the bottow area of the lens. The Crystal Vision polycarbonate, flat top 28 bifocal has a reading area that is 28mm wide at the top. This is a good choice for prescriptions over +/-6.00 sphere. This lens is available in the following range: -9.75 to +5.00 sphere, -3.75 to +3.00 cylinder, and up to +3.00 add (prism and slab off excluded). This lens is also available in the Flat Top 35 style. For the Flat Top 35 style, the reading section is 35mm across thte top. All Crystal Vision Lenses are made in the U.S., to exacting specifications, in an Essilor laboratory, and we are able to offer them at a great price point. This lens is a good choice for corrections up to +/-6.00, and it is available with a variety of options such as Transitions, UV protection, sunglasses or fashion tint, standard Anti-Reflective coating, and the top-quality Crizal Alize and Crizal Avance coatings. All of our lenses come with our Perfect Lenses Guarantee.