Prism form: Base up,base down,base in,base out Specifications Sphere: 0.0 to -29.50 Diopters, step: ... ± 8.75 Diopters,step:0.25 Prism form: Base up,base down,base in,base out Binocular balance: Rotary prism,polarizing filter and R ... /60HzHorsepower:90W Package dimensions:590×470×470mmGross weight:15kg Integrated automatic refractometer