Paul,
Those are banana plugs. They are used in a lot of audio applications. You can get a nice tight wire conection on the plug and just plug it into the TIU. Much easier than wrapping the wire around the post and tightening the nut. They also make it easier to disconnect the TIU. You can get them as single plugs or a double plug well well as multiple styles. The double plug works well on the TIU as well as the Z4000.