Samples for cryo-electron microscopy (cryo-EM), and cryoelectron tomography (cryo-ET) were mixed with BSA coated Accessories, Wageningen, The Netherlands) at a ratio of 2:1 (virus:gold) for cryo-ET, and (9:1) for cryo-EM. Specimens (4 ml) were then applied to glow-discharged quantifoil grids with 2 mm holes spaced at 1 mm intervals (Quantifoil MicroTools GmbH, Jena, Germany). Grids were subsequently plunge cooled in liquid ethane using a Vitrobot Mark IV (FEI Company, Hillsboro, Oregon, USA). Specimens were transferred to a Tecnai 20 G2 transmission electron microscope (FEI) operated at 200 kV, equipped with a Gatan CT3500TR single tilt rotation lowtemperature specimen holder. For cryo-EM imaging was conducted at temperatures of ,2185uC. Images were recorded using an Eagle 4K CCD camera (FEI Company, Hillsboro, Oregon, USA). For single particle image analysis, images were taken at 50,0006 or 80,0006 magnification at 2-4 mm defocus, with a dose of 10 electrons/Å 2 . This corresponded to a pixel size at the CCD detector of 2.147 Å /pixel and 1.353 Å /pixel, respectively. For virus length measurements low magnification cryo-EM images were taken at 5,0006, 3,5006 and 2,5006. For cryo-ET single axis tomograms were taken at 25,0006, 29,0006 or 50,0006 magnification, at 28 m or 26 m defocus, with angle steps of 2u24u. Data were collected within tilt ranges of 660u, or 652u, with a total dose/tomographic data set of 47-60 electrons/Å 2 . For cryo-EM, data collection was done using the low-dose unit and software coupled with the TEM Imaging & Analysis (TIA) software (FEI Company, Hillsboro, Oregon, USA). Automated eucentricity determination, and focusing were performed using the Xplore3D data acquisition software (FEI Company, Hillsboro, Oregon, USA). For cryo-ET, data collection was done using the Xplore3D data acquisition software, the low-dose unit, and the TIA software (FEI Company, Hillsboro, Oregon, USA).