Our mud flaps are cut with CNC technology. Our lasers are incredibly precise, but because the material is being cut with heat, from time to time you will see small waxy line of "slag" on some of the edges (such as around holes) on the tire side of the mud flap. This is part of the manufacturing process and is considered to be normal. In most cases this slag is only visible until installed, at which time the hardware and vehicle will cover things up.