6aluminum, anodized, irregular shaped, channel type, 5.560 in. Lg o/a, 4.620 in. W o/a, 2.500 in. H o/a, 0.660 in. Thk flanges, 1.172 in. Min, 1.188 in. Max w between flanges, 4.000 in. H of flanges, 0.635 in. Min, 0.644 in. Max hole drilled through both flanges