I hope this information helps: I just installed this yesterday on my Chevy 2500HD. The instructions could be better but I've seen worse. First, the kit includes two sets of hex head (allen wrench) bolts. it also includes a spacing block that is NOT needed on 2500 and 3500 trucks. You only need the longer bolts if you use the spacing block. Use the shorter bolts to assemble the step before installing it on your truck bumper. Now on to the bumper area. There are two metric bolts under the rear end that help attach the bumper to the truck. You MUST remove both nuts from the bolts because the bolts are connected to each other on the bolt head side with a metal strap that was not easy to see. I used a rubber mallet to tap the bolts free after I removed the nuts.The existing bolts are about 1/2 too short for mounting the step. They are size: M12 and about 1 3/4 in length. You will need to supply your own replacement bolts in order to mount the step. I think the SAE version is 7/16 but I didn't have any on hand so I had to go to the nearby hardware store for bolts. I found M12-1.75 X 50mm bolts that fit perfectly. I was able to reuse the existing nuts. Just in case, I added M12 washers to the bolt head side. I was able to use an 18mm deep socket when reattaching the nuts but the bolt heads required a 19mm wrench or short socket.The step was in line with the bumper (not crooked as some other folks have said) and seems very sturdy. It folds almost completely under the bumper. I am pleased with it so far.
Rating: [5 of 5 Stars!]