All the pics i see for the ERK cargo compartment trim show a black trim in the bed with wood strips. Is this a plastic liner or is it carpeted? What are the 2 bed track covers? Are these along the pickup bed rail for the bed lid? I've never seen tracks for a bed lid....I have one on my Silverado pickup with no tracks. I noticed that these come painted if ordered with the ERK trim group but if you order through parts they have to be painted. Any input is appreciated.