I have a 2017 nitro z20. There is a black plastic piece on the rear deck behind the side compartments on each side and they’re the size of a nickel or quarter and they’re in the gunnel. I believe they are just to serve as a little vent. I had one fall out yesterday on the way home from a tourney and now it’s just a little hole and driving me crazy. Not sure the part number or even what it’s called to try to get another to replace it. I have pics of it but came seem to figure out how to upload pics anymore. I’m going to keep trying. TIA for any help!