That makes sense that maybe it was only from the factory on the very last ones made. I never checked to see if was the only one listed on the later ones, so maybe it was supplied as an update for the earlier vehicles ?? That's the kind of thing that can get interesting when you start having the axle rebuilders mixing and matching and boxing stuff under the same axle number. I put the hard boots on my type A axle but had to squish down the small end with the clamp so probably will fail there. I meant to do something different to get around the squishing on the second boot but was in too much of a hurry so that didn't get done. Both holding up well though so far