The Bontrager fenders\mudguards actually are really nice and are designed to fit the Treks bikes. I have some on my CrossRip as I used it for a Commuter\Rain bike. They also will fit my Domane and will work on my wife's FX4. You will just need to make sure the tire size you are running, work with them. There are 3 sizes. The one I use for my CrossRip work up to 35's and I am running 32's on it.
