The ones that I've seen that we know slipped (motor won't run with the marks aligned, but seems OK if you tune it "by ear" and check for pinging - including my 250), all look worse than that (more rubber, more out from only 1 side, both), but this obviously only catches them when they're toast. If you can rotate it by hand (strap wrench; I use a seat belt), or wiggle it front to back, it's gone.
I know nothing about any aftermarket except that NAPA probably doesn't carry anything too bad.
It's important that this be fixed, because the harmonics occur in narrow RPM ranges, and cruising in exactly that spot for an hour might throw the ring right off (into the belt, blah), and certainly not protect the engine.
