Performance of a force field can be assessed by comparing different observables between relevant experiments and MD simulations. For membrane lipids, the C-H bond order parameters S CH offer an appealing option for such a task since they can be accurately measured experimentally using 2 H-NMR or 1 H- 13 C NMR techniques, and easily and directly be calculated in MD simulations. The S CH have a long history in force field validation for lipids and a large amount of experimental data is available in the literature . Finally, as S CH can be calculated for every C-H bond of the lipid molecule, they offer a very localized picture of the possible deficiencies of the simulation model .