Board is a 2"x8"x8' and the sides are 1"x4". If you want a wider ramp you can use two of the aluminum flange on a wider board or two boards screwed together which should also give you double the load capacity. With my single setup I have loaded 500# street bikes with no problems. My current bike, W650, is lowered an inch at both ends and clears the ramp with no problems with the tailgate removed, my truck's rear end is also about 2" higher then stock because I have RoadMaster spring assist installed.
here is what mine set up looks like:
you can see how I have the angle cut to clear the bike as it gets to the lip/flange/top of the ramp and also the hex screws I put in to give traction:
with out tailgate: