Peak Vision GS4.01 Sunglasses, Black Dual Zone technology optimizes vision across lighting extremes such as bright sky and dark grass PEAKS Dual-Zone/Zero Distortion Lens Technology prevents bi-refringent distortion and reduces Chromatic Aberration (Lens Clarity, high 45 abbe value) Eliminates optical errors common with Polycarbonate Lenses such as Bi-refringent (rainbow appearance) and Chromatic Aberration (Lens Haziness)