Many indoor carpet venues require that the shock towers have a guard on them to prevent the sometimes sharp shock towers from tearing or damaging the carpet. Not to mention that a little protection on these shock towers can prevent expensive breakages and keeping them in good condition increases the resale value of the car.
Direct replacements for part number #91885 The Shock Tower Covers.
These are made from TPU, which is flexible and more hardwearing than the standard plastic part. Also, the kit part is a rather understated Grey, whereas these are a nice bright blue or red colour to accent the car and give a distinctive look.