Explore the sea like never before with the Alder Full Face snorkel. Allowing 180 degree view and with a built in snorkel and GoPro mount. The Dry Top snorkel stops any water getting in while you dive to explore the depths below. Measure from the bridge of the nose (between the eyes) to the bottom of the chin If less than 12cm- S/M If more than 12cm- L/XL