Normal Tongue Masks
For Masks with normal tongues, you will be required to use a strap that doubles over like in the photo. This is applicable in all competitions and is encouraged at a club level.
An advantage that this system has is the adjustability coupled with addressing some safety concerns. Traditional elastic is subject to stretching an no longer functioning as intended. This system is easier to replace frayed elastic from excessive use.
Leon Paul Dome Mask
For Leon Paul masks with a dome back, you are required to have 2 safety systems securing the mask to your head. You require both the overlapping elastic strap which has both of the same benefits as mentioned previously.
The other system that you need is a second strap that affixes to the bib of the mask. Leon Paul sell a proprietary strap with magnetic ends that allow you to easily strap up and remove with one hand.