Sherwood Ceto MaskCeto Mask The Sherwood Ceto mask is a colored enhanced single lens frameless mask with a durable silicone overmold. The Tangine lens or orange lens was designed to offer optical contrast while diving. The Tangine lens drastically reduces light wavelength from 400 600 nanometers. This minimizes the UV light entering the mask which reduces glare and improves optical clarity. The Rubicon lens or red lens was designed to add more optical contrast and make