These bleachers have aluminum understructure and anodized aluminum 2 in. by 10 in. seats and double 2 in. by 10 in. mill finished floor planks (to meet the new code regulations). They have a front seat height of 16 in. and a back row height of less than 30 in. so that guardrails are not required by most building codes. The four row bleachers have annodized aluminum 2 in. by 12 in. seats, a front seat height of 10-1/2 in. and back seat height of less than 30 in. Guardrails are not required by most building codes for four row bleachers. The five row bleachers have a chain link guardrail across the back and down the sides to row three and 2 in. by 10 in. riser planks on the top row. The 3 row bleachers have a depth of 4 ft. 10 in., the 4 row a 7 ft. 1 in., and the 5 row a 9 ft. 4 in. Bleachers are shipped knockdown for assembly on site.