OK, if you have the stock JDM mirrors, with the spring loaded base, you need to drill the holes just like I showed you in the instructions, no bigger, no smaller....the big plastic base with the metal plate goes in from the bottom, underside of fender top. no need to drill into the frame anywhere....the small hole is for the indexing pin, this keeps the mirror from turning on the fender once installed. once you drill the two holes, simply place the plastic trim base on the top of the fender, line it up in the holes you drilled and then place the mirror mounting bolt(the long one) down through the big hole and then from the underside place the base (big plastic thing with spring in it) up on to the long bolt and start the nut on the mounting bolt, then check that everything is lined up...ie indexing hole and pin, base, mirror and then tighten it down till the nut stops on the bolt.....that's how i installed mine, my fenders already have the holes, its a JDM car, but once you drill your fenders it will be exactly as mine installed....no difference. I would do it all on the car....and i did it with 17inch wheels on the car....wasn't hard at all. When its all tightened down, they should flex outward a little,, that's the design....kinda like break-away....but they should be fairly tight on the base.