Does the nautilus BVC coil grommet replace this one? In that case, would try to pry this one out, have some bvc coils hanging aroundAll of my 510 grommets on my Siren's had to be pried out from the bottom before I could get my screw driver up in there to tighten the air post. I would put a small pointed tool in the center of the grommet and pry it up, then move the tool to the other side and pry up again, and keep at it till I had enough grommet exposed to grab it with a small pair of needle nose pliers and pull it out. Took me about 15-20 minutes the first time to do, but since then it takes me about 5 minutes to get that grommet out of the bottom of a new Siren.