those are plastic pieces that aren't supposed to come out when you pull the armrest off. they are supposed to stay in the door because when you pull that armrest off, you are supposed to twist the armrest to slide the flat parts of those threads out of hte plastic piece. its slotted for the threads to stay tight in one direction and slide out at a 90 degree turn of the handle.
but, if you don't have the manual, you are pretty much stuck finding that out on your own.
the part is called an armrest mounting clip.
the part number is
55215152
i cannot find it though because its discontinued
also, here is the link for the part numbers for your cool seats to get the cover matieral
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i had those seats in red in my commanche and they were super comfortable