With Hydraulic or electrical chair, lower noise when up and down movement. Black, grey, blue color chair at buy's option. - Update: 2007-07-06

1. Ranges of measurement: 0 toA?25D Minimum: 0.125D graduation up to A?5D 0.25D graduations over A?5D to A?25D 2. Cylinder Axis Range: 0 ~180A?step 5A? 3. Prismatic Power Range: Prism Diopter of Pattern A: at 1a?3interval in the range of 0~5a?3Pr... - Update: 2009-06-24