Just had to dismantle the headset on my carbon bike for the first time, it was getting a bit clicky after 18 months of neglect. Dead easy to get the sealed bearings out, just pull out with fingers. Lower bearing has some external rust obscuring some of the markings. Top bearing is TH MR121.1-1/8 45X45. Lower bearing is TH MR168.1-1/4 and also looks like 45x45? Bottom bearing wasn't bad but I suspect has had some water in it and is slightly notchy. I popped off the seals and forced in some fresh grease so it will live a while longer yet. I want to get some replacements ready for the next time and can find normal, standard bearings no problem. My question is, should I be looking for something better or more durable? I have seen stainless steel versions which I guess would be good because it seems to be water ingress & corrosion that is the problem rather than wear & tear. I have searched the forum and can't find any threads about this but I can't be the first person in this situation. Does anyone know which bearings are best and why?