I use Duralast from AutoZone. They are lifetime replacement and I plan to keep this thing forever. They are actually good quality too with minimal brake dust.
I love my KM3's
I do a lot of highway, and when I get the chance to take it off road, I don't hold back. They are great in every way, and they balance out very well with no vibration or shake on the highway, even above 80mph.
Initially I heated mine and moved it, but just spend a little and get the Ark Splash Guards. They looks great and offer better coverage and fitment.
Code TRDHULK gets you 10% off. They offer rear mud flap deletes as well.