I know nothing about cars, and it caught my eye.

 

Rubber? Just a liner to help wind resistance and keep crap out

 

I think you are talking about the air damn that connects to your fenders and is for "aerodynamics" But i am not sure as the pictures are not very reviling

 

Yet you own an XJ... I suggest you start learning! there's always something to do on a Cherokee

 

Haha okay thanks

 

It's a rubberized felt, used to keep debris out of engine compartment. And help with undercarriage air flow. If the mounting holes are enlarged. (ripping or worn) Just make larger fender washers out a plastic milk jug. And slip them under the head of the black plastic retaining buttons. That's what I did. JMO!

 

It's a diaper. If it's sagging, it must need changing. (JK )