Å for a pure lipid system to 97 Å for pure PBd22-PEO14 vesicles. Overall, the bilayer thickness measurements from cryo-ET intensity profiles and SAXS electron density profiles for pure lipid and pure polymer membranes found in this investigation broadly corresponds with measurements determined previously by cryo-TEM, SAXS or SANS and simulation. Here, the hydrophobic thickness of the membrane, previously under-considered in cryo-TEM membrane measurements, have been resolved using cryo-ET, as well as adding new details, including the presence of 2 bilayer populations in POPC/PBd22-PEO14 hybrid samples, which has been utilised to optimise the SAXS model.