Andrew R Stewart 

dsaul says it right. I'll add some terminology advice too- Claris is only a price point/grade/intention of use label. Over time this label remains on the outsides while the component has gone through changes (usually small) as the production continues. So Shimano also denotes these differences within any one name with model numbers. These numbers are specific to one version. (Think of it like car names. The actual car has evolved over the years although the name remains the same). This is why including these model numbers is important to narrow down the possibilities to just one.


As to the pulley replacement be aware that as an indexed system the upper (or guide) pulley is different from the lower (or tension) pulley. When buying them make sure they are index compatible (as well as have the same tooth count and bushing width/cog count as the original). When installing them take care to not mix up their proper locations. Andy.