THIS TUNNEL IS MADE FROM 18 GA. COLD-ROLLED STEEL. STANDARD SIZE IS 36" LONG; 10" WIDE AND 9" TALL. IT CAN EASILY OVERLAP SO YOU CAN MAKE YOUR TUNNEL ANY LENGTH YOU NEED. THIS KIT COMES WITH (2) 1.5" X 1.5" X 36" ANGLES THAT CAN BE USED TO MOUNT THE NEW TUNNEL TO YOUR FLOOR IF NEEDED.