A factory fender flare is trim placed around the outside of the wheel well to both protect the vehicle from grime and road debris and enhance the vehicles appearance. I have added a typical photo of what fender flares look like.
The WeatherTech Mud Flaps # WT110005-120005 you referenced are compatible with your 2003 Chevrolet Silverado if they have the factory fender flares. I have provided links to the installation instructions for these mud flaps.
If your truck does not have the fender... view full answer...
The Buyers Products Mud Flaps - Black Rubber - 24" Wide x 20" Tall x 1/4" Thick part # 337B2420LSP that you referenced are in fact reinforced with fibers running through them. I went to look at the ones in the warehouse and they are very heavy duty and will do a great job! The folks behind your will also be very pleased.
I've included a link to the video Ellen did to give you an idea of how they look and feel. view full answer...