> The minimum measurement grid: 0.12D.> The vertex refraction measurement range: -20D Ë +20 D.> Measuring the maximum diameter of the lens: 20mm-85mm.> It's easy to operate, convenient in use and full in function.> It's portable and convenient to test in hand or on desk at anytime and anywhere.Product Specification :Operation Mode : ManualPower Consumption (Watt) : 3 vColor : WhiteVoltage : AC & DC SupplyTarget : Direct Scale Reading System Cross Line TargetSphere Power : +-20Power Supply : 220v / 110vHandling : PortableType : Direct scale reading systemTarget : corona TargetVertex Power Scale : 0 to +- DioptersGraduations : 0.25D Graduations upto +- 20DPrism Diopter Scale : 0 to 5 Prism DIOPTER, 1 GraduationProtractor Scale : 0_180_ 0 5 Graduation on main scaleHolding Capacity : 30mm to 80mm Diameter LensesTilt Angle : 0 to 90 AdjustableDimension : 300(L) x 150(W) x200(H)mmWeight : 2.5Kg.(appx.)Power Source : 2x1.5VAA size Dry Cell(or) 220 Volt AC SupplyIllumination : 2.3 Volt Manual Lensometer