Otra Backstreet TortoiseshellOtra Backstreet Tortoiseshell .. With a bold, curved tortoiseshell frame that follows the contours of the face, these sunglasses create a dynamic, almost futuristic silhouette. Paired with warm brown lenses. frame colour Tortoiseshell lens colour Brown lens category Cat. 3 frame width 140 mm 5. 5 in frame height 39. 3 mm 1. 5 in nose gap 18 mm 0. 7 in