Which Master Link for my Trek 520

[Figaro]

Ok, I know this may be a nob question, but am collecting bits and pieces for my TransAm trip this summer. Want to carry a couple master chain links just in case -- have never had a chain break, but just in case. My bike is the 2017 Trek 520 and the specs say it has a KMC X9 chain. So, would this be the right master link for that chain? Thanks in advance.

https://www.ebay.com/itm/KMC-Bike-Chain-Master-Links-for-9-Speed-Chains-Quick-Connect/112702310577?epid=691339399&hash=item1a3d94c8b1:m:mmJcDWJESaStWy7sHzfCZOg

[RussSeaton]

You have a 9 speed chain.  So use 9 speed master links that you snap together and unsnap by hand, sort of.  Doesn't matter what brand as long as it is 9 speed.

[Figaro]

Thanks Russ....I assumed that was the case, but I guess I'm old school or just way out of touch with terminology these days. I don't get how "9 speed" equates to my bike when it has I think 21 speeds or gear combinations (7 sprockets in back and 3 in front) At least I think it's 7 in back...just realized I've put well over 1,000 miles on it since September, but never actually counted the number of positions I have on my right shifter :-)

[Pat Lamb]

Sounds like you need to count, and it's easier to count cogs without making a mistake than shifter clicks.  Just remember, chain width is related to number of cogs, and the quick link should match your chain.  That is to say, if you're running a 7 speed chain, a 9 speed quick link won't fit; use a 7 speed link instead.  Likewise, a 7 speed link will stick out of a 9 speed chain and get caught on something.