All aluminum seat planks and steel under structure provide a lightweight, stable bleacher. Seat planks are 10" non-skid aluminum. Galvanized steel under structure is made of 3/16" x 1 1/2" steel angle. Dual braces and rear stabilizing bar add strength and stability. Choose either chain link or guard rail enclosure. Optional center aisle with handrail is available, please call for pricing. Shipped freight. Made in the USA.