Excellent for measuring: Fusional reserves - which can help in your diagnosis of binocular vision problems. Phorias & squints - which can improve the accuracy of your estimations & monitoring. Box comprising a horizontal and a vertical prism bar. Specification:- Vertical Prism Bar:- With 1/2/3/4/5/6/8/10/12/14/16/18/20/25D. Horizontal Prism Bar:- With 1/2/4/6/8/10/12/14/16/18/20/25/30/35/40DAJANTA