I assume those are for use with the tubing benders in your pic. They'd be good for making multi-angle bends along the length of the tubing.
They are for marking tubing, curved or otherwise. A sharpie fits in the top or side holes snugly. I haven't used them yet but really could have when I was making the second and third row seats for the Burb.
I have been using the bead roller lately as I've been making up custom cooling systems.