Posts on a racetrack keg

I just went to clean up a keg I ordered from Midwest a couple of weeks ago. It's one of the racetrack style where the lid is more of a rounded rectangle than an oval. The posts are different than my other two kegs; there are no O-rings on the dip tubes, the poppets are slightly different, and the posts have plastic cylinder that sits between the keg and the poppet. The plastic piece on the liquid post is broken. How critical is that piece? There's nothing equivalent in the posts on my other kegs. If it is important, and I have to replace the post, what do I need to get? The keg is made by Firestone, but will a standard Firestone post work?

The plastic inserts are indeed critical, but rather than go through the hassle of replacing the entire post you can get replacement plastic inserts here and likely other places as well...

Cheers!

Excellent! Thank you!

Figured I would post here rather than starting a new thread since I have a similar issue with a racetrack keg. I found the plastic inserts as mentioned in this thread, but does anyone know where to get replacement dip tube o-rings for this type of liquid post?