A dense technical diagram displays the mechanical components and instruments of optometry equipment rendered in fine black line work against a white ground. The composition centers on a large phoropter flanked by smaller optical tools, lenses, and testing devices arranged in a systematic, patent-drawing style that captures the intricate engineering behind vision correction. Built from double-wall stainless steel and made to order, holding 20 ounces with a snap-on lid, a standard-cup-holder fit, and wraparound artwork. Your commute carrying original art instead of another branded tumbler.