Specifications:
1) Type: external reading system
2) Eyepiece focusing: 0-±5D
3) Vertex power: range: 0-±25D, 0.125D steps up to ±5D, 0.25D steps beyond ±5D
4) Cylinder axis: 0-180Á, 1Á steps
5) Prism power: 1_steps
6) Prism base direction: 0-180Á, 1Á steps
7) Lens diameter: 16-80mm