Using the general workflow depicted in Fig. , we first calculated the flip-flop rates from all the simulations available in the NMRlipids Databank. Flip-flops were observed for cholesterol, DCHOL (18,19-di-nor-cholesterol), DOG (1,2-dioleoyl-snglycerol), and SDG (1-stearoyl-2-docosahexaenoyl-sn-glycerol). The observed cholesterol flip-flop rates, ranging between 0.001-1.6 µs -1 with the mean of 0.16 µs -1 and median of 0.07 µs -1 , are in line with the previously reported values from atomistic MD simulations . The flip-flop rate of DCHOL, 0.2 µs -1 , was close to the average value of cholesterol, while the average rates for diacylglycerols DOG (0.4 µs -1 ) and SDG (0.5 µs -1 ) were higher than for cholesterol. Flip-flops were not observed for other lipids, giving the upper limits for PC-lipid flip-flop rate as 9×10 -6 µs -1 and for ceramide (N-palmitoyl-Derythro-sphingosine) as 0.002 µs -1 . Thus, the available data in the NMRlipids Databank suggest that the lipid flip-flop rate decreases in the order: diacylglycerols > cholesterol > other lipids including ceramides. However, the amount of data for diacylgycerols (8 simulations with the Lipid17 force field) and ceramide (3 simulations with CHARMM36) is less than that for cholesterol (83 simulations); thus we cannot fully exclude the effect of force field or composition on this comparison.