Chemical Composition Rail R50 (Gost7173-75) and R65 (Gost-8165-75) International Standards as follows : R50 -51.67 kg/m GOST 7173-75 C: 0.54 - 0.82 % Mn: 0.60 - 1.05 % Si: 0.18% - 0.40% ; P: 0.035 % S: max. 0.045 % As: 0.01 % Mix of Mass Share R65 - 64.72 kg/m GOST 8165-75 C: 0.54 - 0.82% Mn: 0.60 - 1.05% Si: 0.18% - 0.40% ; P: 0.035 % S: max. 0.045 % As: 0.01 % Mix of Mass share. Origin: Saudi Arabia.