28a difference between channel steel and 28b channel steel
50 * 37 * 4.5 5 5.44 #63 * 40 * 4.8 6.3 6.635 #65 * 40 * 4.8 6.5 6.7 #80 * 43 * 5 8 8.045 #100 * 48 * 5.3 10 10.007 #120 * 53 * 5.5 12 12.06 #
180×70×9 18 # B 23200×73 * 7 20 #的22.637200×75×9 20 # B 25.777* * 220 77 7 22 #的24.999220 * * 79 9 22 # B 28.453* * 240 78 7 24 #的26.86240 * * 80 9 24 # B 30.628
In general, the same model (same) channel, legs and waist width b thickness greater than a, so the unit length with numerical models of steel, than a heavy B.
