The commuting bike I'm intending to buy has a 7-speed cassette and double chainrings. I have a multi-tool on my shopping list, but the tool I was thinking about buying specifies it's for 8/9 speed chain.

http://www.nashbar.com/bikes/Product...4_10000_200502

(I have one of these that I carry on my Surly LHT.)

Ignorant me, I guess, but I didn't know there was a difference.

Can someone please explain about bicycle chain sizes?

What multi-tool or chain tool should I buy for a 7-speed chain?