Ray-Ban RB4171 Erika Classic M (54 - 18) with Grey lenses 。54mm This frame size is Medium with a hinge to hinge measurement of 132 mm. Ideal for average faces. 100% UV PROTECTION: To protect your eyes from harmful UV rays, these sunglasses include plastic lenses that are coated with 100% UV protection. Lenses measure 54 mm wide, and they are durable and non-polarized. DURABLE NYLON FRAMES: Ray-Ban Erika sunglasses are exceptionally durable. The frame is made from lightweight and durable nylon. The bridge measures 18 mm, and the arms are 145 mm for an easy, comfortable fit. LIGHTWEIGHT LENSES: These Ray-Ban sunglasses feature high-quality, light-weight lenses that help reduce eye strain while outdoors. MULTIPLE FRAME AND LENS COLORS: Choose from multiple frame colors—including black and tortoise—and multiple lens colors and treatment—including polarized, gradient, mirrored and solid lenses.