Steel Flat Bar 3/8 x 12 inch 10 feet - can be cut to le 3/8 .375 teel Plate 9" x 9" x 3/8" Flat Bar Mild teel This website is for sale! Bright Mild Steel Flat Bar (3/32 x 3/4, x 12 inches 1/4 Inch 150mm X 12mm Mild Steel Flat Bar 1/2 Inch Steel Plate 3/8 inch thick (., 375) steel plate.