This is a spare Extension Cable EC-153 for Extension Module EM-153. When you purchase an Extension Module EM-153 it comes with one Extension Cable EC-153. Due to the fine pitch of the connector crimped on this cable that is used to contact the RS-53 Type chips, it is important to handle the Extension Cable EC-153 with care. In case of mishandling this spare Extension Cable EC-153 provides a piece of mind when you need a replacement.