Alcoa aluminum wheels on front ,and the caps?

So I just pulled the R/F wheel off, first removed the plastic decorative lug nut covers then the center cap falls off. Now on my Jeep the center cap goes on from the inside and then is held on by the wheel. Are these center caps the same? Or does the lug nut covers hold it on. They were both done the same time when I had new tires put on so Im stumped on this one. I did put the cap on from the inside, tightened the wheel but it just doesn't look right. BTW, Ford E-450