Yesterday I did some craigslist shopping to get the pieces and parts needed to add racks to my truck topper. I was going to weld up custom racks but liked the flexibilty of these commercial track systems. The towers and crossbars I found are Thule, but the tracks I found are Yakima. Everything I found online suggested the tracks are identical, but that is not true!  The plates used in the Thule system are too thick to nest correctly in the Yakima tracks. Using them like that could lead to serious failure. So, I machined the plates down a little to fit correctly.