The clutch measures 4" and you use a 4" band. It gives you about an inch of contraction.
It's confusing, I know. I bought a 4.5 for my Ruttman and it's usable but it's drawn almost all the way up. So I put a 4 on it and it works much better and it allowed me to put a compression spring on the cable, between the band to aid in expansion.
Randy