Aluminum seat planks and galvanized steel under structure provide the most durable, stable bleacher on the market. Seat planks are 10" wide non-skid aluminum. Galvanized steel understructure is made of 3/16" x 1 1/2" steel angle. Shipped freight. Made in the USA. 15' long bleachers seat 30. 305 lbs. 21' long bleachers seat 42. 425 lbs. Preferred bleachers feature double foot planks and are ALL aluminum.