Segment Height (AKA Seg Height or SH) is the distance between the bottom of your lenses to the top line of a bifocal or the beginning of the addition in a progressive. Segment height does not apply to single vision lenses. Segment height is unique to every pair of glasses. If you’re unsure of your segment height, we use a standard “-2” segment height which fits most wearers. If you would like a specific segment height, please call us after placing your order.