All made from the same stuff.Easy to see how they are fixed once the wheel is off and the car is safely sitting on an axle stand o other solid object......never work under a car held by a jack
They're' not "carpet" they are like a thin scouring pad stuck to some reasonably stiff plasticy stuff. The "scouring pad" surface is supposed to reduce spray and noise. Contrary to myth, they have no effect on rusting.