Original R-50 R-65 Tee rails weighing 50 pounds per yard or more, 6 meters long and more Nominal Specification for R50 â?? 51.67 kg/m GOST 7173-75 Nominal Specification for R65 â?? 64.72 kg/m GOST 8165-75 Nominal Chemical Composition Carbon (C) 0.20% to 0.60% Manganese (Mn) 0.60% to 0.90% Silicon (Si) 0.15% to 0.35% Sulphur (S) 0.05% to Maximum Phosphorous (P) 0.05% to Maximum Arsenic (Ar) 0.15% to Maximum