HP 657401-001 is a DVI-D to VGA adapter listed in HP’s Microtower spare-parts catalog. It is intended to connect equipment using a DVI-D connection with a VGA display connection, making it useful when matching those two interface types.
The catalog identifies the exact part number and distinguishes it from a separate DVI-I to VGA adapter. This is the DVI-D version, so the connector type is an important part of its identity. The source does not specify dimensions or package contents.