OK< I see what you're saying, Ed. The ID page says this: "The measurements listed in the table above are taken from the bottom of the spacer to the fan mounting flange". So you're right, I should use 1 3/8". I'm also going to have to add text that says something like "this might not be the same as what you see in the MPC. We believe the MPC measurement represents the total height". Or we could just use total height, too.