Micrometric buckles together with the notched strap on either side of the mask allow easy and highly accurate adjustment of the mask, even when wearing gloves.
The volume of air inside the mask, between the face and the lens, represents the internal volume.
For freedivers and spearfishers, the internal volume of the mask must be as small as possible to facilitate equalisation.
The mask gets pressed against the face when diving down. As you dive, pressure gets applied to the mask's soft skirt, reducing the internal volume and pressing the mask against the face. This phenomenon, which can cause pain in the eyes, can be avoided by equalising the internal pressure of the mask and the external pressure applied by the water. Simply breathe out gently through your nose. Air is very precious in underwater sports, so this equalising effect must be kept to a strict minimum.
Silicone is an extremely flexible material. A silicone skirt conforms gently to the contours of the face, creating a watertight seal. The material is hypoallergenic.