The FIDUCEO Microwave Fundamental Climate data record, v4.1, contains microwave brightness temperatures and uncertainties for series of satellite instruments (all mission years of SSMT2 on F11, F12, F14, F15; AMSU-B on NOAA15, NOAA16 and NOAA17; and MHS missions (NOAA18, NOAA19, MetopA,-B)). The presented FCDR is a long data record of increased consistency among the instruments compared to the operational data record and is a long enough data record to generate climate data records (CDRs) for climate research. The improvements are based on the strict application of the measurement equation as well as dedicated corrections and improvements within the calibration process. The data record contains quantified uncertainty components, respecting the correlation behaviour of underlying effects. Full documentation including product user guide, tutorials, the scientific basis and relevant publications are available in the documentation