proper way to measure for rear end u-bolt length?

thats what i though.. i wanted 9" which woudl have worked but these measure 10" which are way too long.. looks like 8" would fit perfect. just have to find a set now and return these mis marked ones.
.... or cut em to the length you want. (Die grinder with a cutoff wheel.)

Edit : oops. Didn't see that the threads are too short at first. Yeah, just send em back.
Or add a 1" lowering block, lol.