Ratcheted hinge on lens cover can be raised or lowered as needed. Interchangeable lenses snap into high grade plastic housing. Headband has adjustable strap and foam lining for greater comfort and ease of fitting. 164830 Specs Magnification: 3.0x Diopter: 8D Lens Type: Aspheric Case: no Case Material: no Mount: no Lens Material: PXM Plastic with Cera-Tec Coating Miscellaneous: Fits Over Prescription Eyewear, Replacement Lens is Available (1645-3), Frame is Available Separately (1644-504) Temples: no Temple Length: no Bridge: no Bridge Size: no Frame Size: no Focal Range: 6.4" Rx-able: no Display: no