Moving to the Necromunda section...

I managed to pick up the core boxset and Outlanders at a con over the weekend for cheap. They didn't come with any rules but all the terrain and plastic were still on the sprue/unpunched.
I wanted to make sure I have everything from the main set though, could someone tell me what pieces 13/15 and 15/15 are? I don't have anything labeled that. I think 13 might be the cardboard that makes the square tube at the center of one of the platforms. 15 I think might be another reference sheet.