Drilling:? Yes, one hole on each of the rear flaps, 1/8" into the bottom of the fender, not visible in the photos.? There is a dimple already in place and the screw has sealant on it.? Two holes on each side for the front, these are into the front edge of the running board (plastic), they tie the flap back against the running board so there is no gap.? You are cautioned to not overtighten these, they would strip out fairly easy.? A plastic push connecter would work fine here too, but screws are provided.
Brookie:? I think they look pretty good, but to be honest, most vehicles look better without.? That's just not an option for me, I'm in the mud and rain too much.? I think the best way to look at it is to sight down your door from the window and look at your front tire.? Mud and crud basically can be thrown straight up and can cover your whole door, it can even hit the mirror!? When the flaps are on, looking down the same sighting plane, you can't see the tire until you get back to the back edge of the door.? The flap keeps the crud from flipping onto the door, the mirror, and the running board.? I think it's worth it.
Limnator:? Here's the numbers for a Tahoe, looks like both are different.? Weird, I would think the fronts would be the same:
Molded Splash Guards - Front, No Logo, With Running Boards, Without Fender Flares, Black
? 17802157
?
Molded Splash Guards - Rear, With Bowtie Logo, Black, Without Fender Flares
? 17802159
?