There are several types, or brands available. They all do about the same thing. Some include axle blocks, some are just the adjuster. Bolt Brand adjusters are always a good choice…they match the thread pitch, and the oem bolt head sizes (12mm nut. wrench & 10mm stud, wrench):
Chain adjusters can be a pain if not kept up! They can seize, get stuck, break off, strip, or the heads of the bolts can round out and you will find out that one that has broken off or other wise will become a mess to deal with.
So lets take the time while we are in the area to run these out and keep them clean and lubed up with some anti-seize lubricant.
Permatex makes a good product and a great anti seize lube that you should always have on hand:
Make sure to clean the threads and the swing arm around the axle bolt and axle block area.
Reinstall your new or clean antiseize lubed chain adjuster bolt.
Now if you broke a bolt, that is another story, you can drill out and re-tap the swingarm, I don’t recommend this. You can drill it out, weld it up and have a machine shop tap it out, but this costs money. You can buy a new OEM swing arm, this costs an arm or a leg, but our friends over at CheapCycleParts normally have a good deal going on with the oem parts:
Notice that the hole is not round any more, its very hard giving the location of this hole to rethread, or drill out an old broken chain adjuster. There are some kits available, if you attempt to do this you should buy a swing arm buddy kit: