There are ONIX 2D models and ONIX SI models.
The ONIX SI models come with a single transducer in the box that does Side Imaging, Down Imaging, 2D Sonar and Temp.
It is a transom mount style with transom bracket.
You can customize your installation by adding other stuff if you want/need to.
Humminbird Helix 12 SI, 1198c SI, 1198c SI, ONIX 10 SI NT, 360, RC-1