Year Ended December 31, Commercial Trailer Products Segment 2013 2012 (dollars in millions) % of Net Sales % of Net Sales Material Costs $ 741.8 73.5 % $ 740.2 74.5 % Other Manufacturing Costs 190.4 18.8 % 184.0 18.5 % $ 932.2 92.3 % $ 924.2 93.0 % Cost of sales is comprised of material costs, a variable expense, and other manufacturing costs, comprised of both fixed and variable expenses, includi