A pack of 7 dark Octane chassis in different variations: dark (no color), dark + white, dark + purple (pictured), dark + red (pictured), dark + saffron and pink, dark + sky blue, and dark + teal and yellow (thumbnail). These allow you to equip in-game decals.

I have a full guide for installation and for creating your own custom chassis here: https://www.reddit.com/r/RocketLeague/comments/z0k8wt/the_complete_guide_to_custom_octane_chassis/