Stock 20's center cap issue

[Gsmith223]

I had new tires put on recently and and on the drive home I heard something and hit under the truck pretty hard. I pulled over and noticed that the center cap was missing.
I bought a new center cap from Ebay and confirmed the part number is correct but the thing wont stay in at all. Do these also require a retainer ring of some type or what am I missing?

Thanks

 

[hceptj]

Is this the same one you're referring to?

Does the Laramie 20' wheel chrome plastic wheel insert come off??

Clear... i put it on the insert and also the face of the rim where it seats, to ensure it bonded properly... its a tight fit, so they aren't going anywhere. These will be my summer rims so not worried about ice snow etc.

5thgenrams.com