A rebar clip is provided for joining a larger diameter rebar to a smaller diameter rebar transverse to the larger diameter rebar. In a first embodiment the clip includes diameter reducing tabs extending into upper arches of the clip for engagement with smaller diameter bars crossed on top of larger diameter bars. In a second embodiment the clip includes diameter reducing tabs extending into lower arches of the clip so that the clip may hold larger diameter bars on top of smaller diameter bars. A guide track for a clip applying gun is provided which allows for use with either version of clips and with clips of the same nominal diameter for joining equal size bars.