A simple model is proposed for the molecular weight dependence of the relaxation time spectrum of linear flexible polymers with molecules of nearly uniform length. A systematic approach for determining the parameters of the relaxation time spectrum from dynamic mechanical data, G’(omega) and G"(omega), shows the possibilities and the limits of this model. The necessary parameters are n(e), G(N)-degrees, and lambda(max) for the entanglement and flow behavior and lambda(c) and n(g) for the crossover to the high-frequency glass behavior. Generic values are proposed for polystyrene and polybutadiene of high molecular weight.