There had been some complaints in the past about the fit and finish of guides from MikesXSI was referring to the aftermarket guides? I would take an oem in a second.
At one point I thought there was a problem with aftermarket guides.
If this one is comparable to oem that's awesome.
(It can be very difficult to separate product quality claims from ham handed installation and adjustment. )
These from Gary Hoos Racing (fine vendor and heck of a guy) look, and so far act the part of a great product, but they just haven't been out long enough to answer the long term part. That said there have been a few advances in manufacturing in the last few decades...
I think these are the best answer around since Yamaha quit restocking guides a few years ago. Pretty good chance Yamaha had changed vendors, materials, process in the 50 years since the originals were made.