The front Bumper takes the factory lights and moves them inside the frame and gives a bunch of clearance. Print upside down laying flat with thick walls.
The battery tray will lower your battery 3.5mm to lower your cg or use as a ESC/RX stand if you move the battery forward. Print upside down.
This rear body mount lowers your body in the back 3mm to match the front if body posts are lowered. Looks better and you get a lower CG that helps on sidehills and climbs. Print laying flat.