I need to replace the chain on my 21 speed mtn bike (3x7). The chain on it now is a KMC Z-3J it also has the word narrow on it. I can't find any listing on this chain anywhere including KMC's website. Can someone tell me what chain size I need to replace this with?
thanks

Any 7/8-speed chain will work. Most will be listed as "8-speed" but they are also 7-speed compatible. Shimano and SRAM are the most commonly available.

A good chain is the SRAM PC-58. It is nickel-plated and has removable links to aid in chain cleaning.

Regards,

My favorite is the Wipperman 808 because it's fully nickel plated and comes with the connex link. They're $20 from Lickbike.com. They all seem to work fine, I just like the corrosion protection and bling of a nickel plated chain.

Another good chain is Shimano's IG90 which is typically $15 or less mailorder. You have a lot of good choices.

+1 the PC-58 - kinda like a Mack truck with T-Tops (Master Link), but like HillRider mentioned...there are many good quality chains that will work for your app.

Thanks for the replies people. I'll be going to the lbs today. I've spent several hours the last couple of days reading these forums and have learned a bunch. A valuable resource for anyone interested in bicycles.
thanks again.