Sorry Trent, should have given you more to go on !
It's Stock, and on a Ozite track with jumps ( like a UK style indoor track, which is why I love it !)
So, no dirt to deal with, just some carpet fuzz
I have upped the spring tension a little though on my CO27, so I'll let you know how that works, past couple of years I have done ok with Monsters, so CO should work.