Check the listing for details. Donegan Optical Optivisor DA-10 or DA-7. Condition: New with tags. Listed at 58.95 USD. OptiVISOR is a precision binocular headband magnifier which permits unrestricted user efficiency while reducing eye strain—leaves both hands free and allows three dimensional vision. Used by anyone whose profession or craft requires close accurate work. Can be worn over prescription or safety eyeglasses.Optical glass prismatic lenses: Ground and polished to precision optical standards—bevel edged and mounted in an interchangeable plastic frameIt tilts: Adjustable pivots allow the visor to be tilted out of the way when not needed and at your fingertips when you need magnificationAdjustable headband: Conforms to fit all head sizes—fabricated from a special blend lightweight material. Comfortable when worn for long periods of time.High impact visor: Provides a tough, durable, always-new appearanceGenuine leather comfort band: Padded orthopedic felt adds to comfortItem No. DA-7 has a Focal Length of 6" with a magnification of 2.75 times Item No. DA-10 has a Focal Length of 4" with a magnification of 3.5 times OptiVISORS are available in these assorted sizes please contact us for other options Item No.Focal LengthMagnificationDA-2 20″1.5 timesDA-3 14″1.75 timesDA-4 10″2 timesDA-5 8″2.5 timesDA-7 6″2.75 timesDA-10 4″3.5 times