The Z-9 family of swim masks incorporates the best features of both snorkeling masks and goggles to give maximum comfort and seal reliability. The single-construction skirt adds comfort by evenly spreading the pressure of the seal over the forehead and cheekbones. The replaceable silicone mask strap can be quickly adjusted using the same Ratchet Quick Lock (RQL™) design found in the Nat Geo Snorkeler mask series. A simple pull tightens the strap and the press of a button releases it.