I have a 2012 Trek 7.3 with a headset that has the onset of fretting or false brinelling, not sure which term, it feels notched. The bike literature labels the headset as “Slimstak, semi-cartridge bearings, sealed”. Would something like the attached work as a replacement?
Thanks, Mike

Best is to pull out the bearings and look for some identifying numbers which you can use to do a search for replacements. Before buying new you can try using a thin blade of some sort to carefully pull off the seals of the bearings. Flush out the old lube and gunk and apply some new grease and check it the bearings are smooth enough to keep using. Install the seals and you're good to go.

The pictured headset is for a 44mm headtube, you need one for a 34mm headtube. I would consider the stock headset to be a product that is designed to fail, 1/8" bearings are too small to hold up in a headset.

You want an EC34 headset intended for a 1 1/8" threadless fork. For something really solid and inexpensive, FSA Hammer is a good choice. Or for something a little more fancy with cartridge bearings, Cane Creek 40 is solid. There are plenty of other headsets out there that will work too.

The tools needed to replace a headset can be quite expensive, it would be worth considering taking the bike to a shop for the labor, even if you normally work on your own bike.

There's info that might help you here:
The Ultimate Guide To Identifying And Choosing a Bicycle Headset

What are the expensive tools?

The two most expensive are the headset press and the crown race puller. While it is possible to improvise a headset press, the crown race puller is quite necessary for removing a crown race that is smaller in diameter than the fork crown. You also need a headset cup remover and a crown race setter.

Thanks for your help. This is my daily commute bike, so it is tough to punch out the bearings to make exact measurements before ordering parts, since I need the bike daily. I have pulled the steerer and tried to guesstimate the ID's. Clearly the pic I posted is not wholly correct. The lower appears to have an insertion ID of 44 mm and is a zero stack with 45 deg race. The upper is different, perhaps 34 mm insertion, but not clear, since I thought 34 mm is typical of external cups, not zero stacks. I was hoping that 2012-era trek fx's are common enough that someone would know the insertion IDs and type. It is frustrating that headsets are so varied and trek literature does not give specifics. What the hell is a semi-cartridge and why does the literature not say external or zero stack or internal? Aaaargh!

Regarding tools, I have a good threaded rod and large washers for press fitting. I don't think the crown race is the problem since the lower bearings run inside another cup, i.e. the bearings do not touch the crown race.

Apparently 2012-ish Trek FX's headset use external cup upper (34) and zero stack (44) lower. The lower cup feels rough so I will replace only lower.

Now that I think about it, pretty much all of the FX bikes I've replaced headsets on from this era have been the cheaper 7.2 or 7.1. Not too surprised to see Trek changed up the headtube on the 7.3 FX.

If you grab a ZS44 headset lower that uses 45° bearings, you might be able to get away with reusing the old crown race, though it could be possible that things won't mesh up nicely. You could take just the fork in to get the crown race swapped if that ends up being the case.

If you want some extra durability, you could grab an EC44 headset lower intended to be used with a 1 1/8" straight steerer tube.

You can just replace the lower with a ZS44 set, but you’ll most likely need to replace your crown race to match.

I've done all that stuff easily and successfully with improvised tools. I don't dispute that real tools would be easier to use and would be an expense that would not be worthwhile for the very occasional home mechanic's needs (including myself). And if a person isn't into improvising, it certainly is good advice to have a shop do it.