Hi,
31-60-7-507-403 is approximately 5 mm larger at the large end an 3mm larger at the small end than the 31-60-7-507-402. It's also about 4cm taller as well. Without seeing your vehicle it would be hard for me to understand why the dealer didn't install the 402's. We have more inventory of the 402's than any of the other CV boot kit numbers. After speaking with one of our Master Technician's and my parts back-counter guys they informed me that we have not encountered any issues with the outer boot kit's 31-60-7-507-402. I hope this information was useful.
