specitiones:     theoretical weight
25*25 *3                      1.12kg/m
30*30*3                       1.36kg/m
40*40 *3                       1.83kg/m
40*40*5                        2.95kg/m                          
45*45*4                        2.74kg/m
45*45*5                        3.38kg/m
50*50*4/5/6                 3.06/3.77/4.43kg/m
60*60*4/5/6                 3.68/4.55/5.41kg/m
65*65*6/8                    5.91/7.66kg/m
70*70*6                          6.38kg/m
75*75*6/9/12               6.85/9.96/13kg/m
80*80*6/7                     7.32/8.48kg/m
90*90*6/7/10/13          8.28/9.59/13.3/17kg/m
100*100*7/10/13         10.7/14.9/19.1
120*120*8/10                14.7/18.2kg/m
130*130*9/12/15          17.9/23.4/28.8kg/m
150*150*12/15/19         27.3/33.6/41.9kg/m
175*175*12/15               31.8/39.4kg/m
200*200*15/20/25          45.3/59.7/73.6kg/m
250*250*25/35                 93.77/128kg/m