The prediction of linear viscoelasticity (LVE) based on molecular "tube" models, and more recently, atomistic simulations has received tremendous attention in recent years. Major progress has been made, to the point that quite accurate quantitative predictions can now be made for linear polymers, including inverse predictions of molecular weight (Mw) distributions from knowledge of rheological properties. One of the key tube model parameters is the molar mass between entanglements, Me.