Nordyne combustion blower assembly for many M1 models. Brings air for combustion to the burner. 115V. When looking inside the assembly, it contains two blower wheels (white and black). Outside diameter on end with white wheel is 5.5". Outside diameter on end with black wheel is 5-1/8". Length of complete unit is 7-7/8". Flow probe included and installed. Male 2-prong molex plug. Replaces 621787.