Hands-free optical binocular magnifier with a precision ground and polished glass lens is for use on viewing items 4 inches away. Powerful 3-1/2 times magnification makes this great for viewing fine print or small items without eyestrain. Adjustable frame is made of lightweight, durable impact-resistant materials. Pivot knobs can also adjust to hold visor in any position for easy flip-up when not in use. Can be worn over prescription or safety eyeglasses. Additional lenses either for replacement or an alternate power, are available separately.