I had my nephew help me put together the side rails and help me lift the Retrax MX Pro ( new matte black) regular rail width onto my Denali this morning. Everything went together very easily, after we put it in, you have to measure the inside width, front, middle and rear. If is wider or narrower, you adjust the width with plastic set screws , then clamp it down with the 4 included aluminim C-clamps. And pull the rails back to within 1/8" of the tailgate, they give you a little plastic shim 1/8" to use as a measuring guide. Easy...
The only problem was before we could put the whole Retrax box in, we had to take out the two front stock tie-downs. You unscrew them while pullin back, then grab the springed wing nut. One of them fell down into the inside wall, damn... Tomorrow, I'll try to get it out with a long flexible magnet thingie.
Not counting that, everything went together smooth.
It sure looks great! And slides back and forth nice.