... tip of the instrument for more light output, less glare.2. 2.5 x ... design and comfortable operation.3. Suitable for small pupil.4. 19 lenses from 0D to ±20D: 0D ... Aperture wheel: red-free filter, Large spot, small spot, hemispot.Technical Specification:Name of aperture Dimension ... ±15D, ±20DAperture: red-free filter, Large spot, small spot, hemispotRated voltage: AA alkaline or Ni-MH batteriesElectrical ...