COOL FACTOR A field of view so wide you can see your tank valve. key features A different take on the three-lens mask, the Visio Tri-Ex uses domed side windows to increase the field of view out to a wide 168 degrees. Creature comforts include a three-dimensional mask strap that conforms to the diver's head for a more secure hold and a round-edge skirt that seals well on a wide variety of facial types.