"Exact error threshold for Eigen model with general fitness and degradation rate functions."
We derive exact analytical formulas for the error threshold of Eigen model with rather general form of fitness and degradation rate functions. For the some case of degradation rate the known quasispecies error threshold formula is modified. For the neutral mutations we rigorously derive the degree of selective ability ("neutral fidelity"), revising the known formulas in neutral evolution. It is possible a mutation threshold phenomena for the neutral fidelity.