I had a lot of trouble getting mine to fit. In the end, I had to file away most of the inner lip to reduce it to the three retainers and then cut one of those back to get the clearance. However, once on, it has stayed in place very well. After a bunch of measuring I found that the tunnel casting was a bit rich and no amount of fiddling would make the ring fit. Rather than filing the tunnel cover, filing the ring was a better option.