As you can see by the photos, it is noticeably larger in diameter and the bore in the hub much smaller. ..clamped down gingerly on the mill, indicated center and set up the boring bar. Measurement of the hub assembly on the car shows we had to rebore the larger diameter to a depth of .135" in a flange that had a body diameter of the same size, so that meant that we'd be cutting that overbore, over half of the thickness of the mounting flange. As for the fan itself, a perfect fit .