Polyurathane Leaf spring bushings question??

[amodedude1]

One last question that is annoying me with this.... What is the difference between the main eye and the frame shackle eye?

I know it should be straight forward but I was assuming the main eye was the eye on the leaf spring itself. Many of the vendors are only selling kits with a 1 3/4" "main eye". I measured 1 1/2" on the leaf spring eye, which I took to mean "main eye", do I have main and frame shackle eye's confused or am I good?

Thanks again!