It is the category where an inexpensive part makes the largest visible difference to a used interior, and also the one where water damage hides.
Floor mats wear through at the heel pad, carpets stain and hold moisture long after a leak has been repaired, and cargo liners crack at the fold. Because the carpet sits on top of the floor pan and the sound deadening, a damp carpet is usually the first sign of a leaking windscreen, heater matrix or door seal, and replacing the carpet without fixing the leak simply repeats the problem.
Match by body style and by drive side. A carpet for a left-hand drive vehicle has the pedal cut-outs on the other side from a right-hand drive one, and a wagon carpet is longer than a sedan carpet. Mats are matched by model year and by whether the vehicle has retention posts.
