Fig. 3 A. Flat-top (FT) trifocal, specified by vertical dimenshon of the intermediate/largest horizontal dimension. Available as 7/25, 7/28, 7/35, 8/35, 9/35, 10/35. B. An executive trifocal, available with vertical intermediate dimension of 7 or 14 mm. C. E/D trifocal. Intermediate vertical dimension of 8 and FT width 25. D. Double-round segments. Vertical separation 14 and diameters 25. E. Double executive. Vertical separation 14. F. Double FT. Vertical separation 14 or 15. Segment diameter 25 or 28.