This is my prototype, temporary "Monitor Series" center channel speaker.
The pink you see on the right, in the port, is plugging the port. The pink you see above the left 6.5" driver is there to hold the grill in place (obviously the grill isn't shown). The pink you see in the left-hand port is actually the lining inside the speaker.
I don't know how to post multiple pics, so I have to use another post....
This speaker is a 'new' SL2000, two 6502s, and the crossover from an RTA8. Sounds great, and can handle more power than the small Advent center I was using.