ML3DBSO2 is the EOS Aura Microwave Limb Sounder (MLS) daily binned on various vertical grids product for sulfur dioxide (SO2) derived from radiances measured by the 240 GHz radiometer. The data version is 5.1. Spatial coverage is near-global (-82 to +82 degrees latitude) at a spatial resolution of 4 degrees latitude by 5 degrees longitude. The recommended useful vertical range is from 215 to 10 hPa, and the vertical resolution is about 3 km. Users of the ML3DBSO2 data product should read chapter 4 and section 3.21 of the EOS MLS Level 2 Version 5 Quality Document for more information.The data files are archived in the netCDF4 format, which is also compatible with HDF5 readers and tools. Each file contains six group objects: lat-lon map vs pressure, lat vs pressure zonal mean, lat-lon map vs theta, lat vs theta zonal mean, equivalent lat vs theta zonal mean, and vortex average vs theta. Each group has a set of data (average, min, max, std dev, rms) and geolocation fields, grid attributes, and metadata.