Hi Mike, this came from 2021R1. It looks like sqrt(2/3) will create the right value though according to the mesh diagnostic (whoops this may have been a typo on my end). Regardless of that, If I set a model to have no contacts, one linear hex, use a time safety factor of 1, add a simple displacement to the element and solve, then time increment in POST still does not equal t = (1)*L/c . Am I missing another factor or is CFL just a starting point to work from?