Originally Posted by
dsbrantjr
"you can get away with a few cm"
Watch your units, a few mm is more like it.
Yes, it's a very specific 4.5mm for putting a 7 speed cassette on to a 8/9/10 speed Shimano hub. Here is a link to one at Harris Cyclery, any good LBS should have / be able to get them
http://harriscyclery.net/itemdetails.cfm?ID=2127 &
http://sheldonbrown.com/harris/parts.html