Originally Posted by
VegasJen
And as long as we're on the subject, how do I identify this chain? I mean identify it for the correct replacement. Yes, it's dirty, but it's not in bad condition - yet. But I would like to have a spare on hand, and if I end up getting that larger cassette, I will likely need a longer chain anyway. All I have found on it is the "IF". Otherwise, nothing else that might tell me what size it is.
Any 10-speed chain should work, but some believe that matching cassette and chain brands allow better shifting; since you are buying both a new (larger) cassette and a chain, you might as well buy a matching chain.
No SRAM experience here but both (a) your photos above -- which show a relatively short RD cage -- and (b) your prior mention of an existing 11-25 cassette suggest that (1) your current RD has a short cage and (2) you will need a new RD with a medium cage to run a cassette with a largest cog > 28T.
RED Rear Derailleur 10-Speed | RD-RED-B1 | SRAM
(An SRAM Red RD but may not be exact RD you have; included just for reference to 28T max cog size.)