The straps are elastic with beads so that they can be adjusted and they go behind the ear. All masks are made of 100% polyester with a pocket where you can add a filter if you want. These are the average sizes for the masks: • Small - 8inches(width) x 4.5 inches (height i.e. from chin to nose) • Medium - 8.5 inches x 4.75 inches • Large - 8.5 inches x 5.25 inches • Kids - 7.5 inches x 4inches All straps are adjustable...