Originally Posted by
Torchy McFlux
5/6/7/8-speed chains share the same dimensions and are pretty much interchangeable.
Not quite. 7 and 8-speed chains are the same width and interchangable. In the past they were referred to as "narrow" or "ultra" chains.
Older 5/6 speed chains are wider and don't work properly on the narrower 7 and above speed cassettes or freewheels. However a 7/8-speed chain will work fine on 5 or 6-speed freewheels.