ポリ塩化ビニル
Two of the panels are perforated along adjoining edges, so that they can be laced together. One of these lacing panels receives an additional perforation and reinforcements in its center, to hold the inflation valve. Each panel is attached to an interior lining. The four panels are then stitched together in an "inside-out" manner. The edges with the lacing holes, however, are not stitched together. The ball is then turned right side out by pushing the panels through the lacing hole. A polyurethane or rubber lining called a "bladder" is then inserted through the lacing hole. Polyvinyl chloride or leather laces are inserted through the perforations, to provide a grip for holding, hiking and passing the football. Before play, according to the NFL rules, the ball must be inflated to an air pressure between . The ball weighs .