Just finished mine. 14" of 4" ABS, two caps, and stainless hardware. The rest is cutting and so on depending on what you have to use for mounts. Mine was square tube. "Compared To What" (screen name) did one that came out real nice.
Finished project! Forgot to mention, the rack system is Caribou/Pelican. Made the forward bracket to fit between the two pieces. Only hole drilled was for through bolt for the back mount. It will be different for other rack syatems.
Hope that helps!