These cylinder geometries are used to verify models in HemeLB. They have cross-sections approximated by 128 edges and feature radius-to-length ratios of 1:10 for cylinder.stl and cylinder_deg20.stl, and 1:20 for cylinder_extended.stl. The cylinder.stl geometry is aligned along the z-axis, while cylinder_deg20.stl is a 20-degree rotation of cylinder.stl. Provided in STL format, these geometries are defined with arbitrary units. Users can create the simulation domain for HemeLB in GMY format from this geometry by using the voxeliser available here.