Speedo Adult Hyperdeep Mask/Snorkel Set Rigid interlocking frame creates added support Speed Fit clips allow for quick, easy adjustability while silicone mask skirt offers a comfortable long wearing, watertight seal Tempered glass for improved saftey and clarity, with wide angled lens to maximize peripheral vision Dry Top snorkel keeps water out, purge valve removes water quickly Soft silicone mouthpiece with attached safety whistle to notify others from a distance