Cummins 4B3.9/6B5.9 Air Compressor 3964688 Parts Catalogue Ref No. Part Name Part No. Required 1 Air Compressor 3964688 1 Above is the introduction of the Cummins 3964688 Air Compressor, while if you need any other Cummins spare parts or complete Cummins engine, Please further consult our sales.