I ordered fenders from Trek for my 2008 (? I think) FX 7.2 with 700 X 35 tires. In looking on the Trek website I noticed there were several sizes, and I "assumed" (yes, I know what happens to people who assume) that a fender characterized as 700 X 35 would fit a tire of that size. But, so as not to be presumptious, I called rather than order on-line, and the idiot taking my order assured me that my "assumption" was indeed correct. But when they came, the fenders are the same size as the tire. No way they will fit. What bike measurements are used to properly size fenders?