I think the Duke 3 and the Chubby 1 has the same knot size with different handles.
Originally the Duke and Chubby were NOT just different handles - I can assure you of that!
Density is a major difference as well. The chubby line is probably one of the densest brush lines made.
The Duke 3 and the CH1 range all have very similar, if not the same knot.
I have a CH1 in 2-band super and one in 3-band super as well as a Duke 3 in best. With the particular specimens that I have, the least dense of these is the 2-band super followed by the Duke 3 and the CH1 in 3-band taking the lead for the most dense.
Great brushes, the D3 and CH1 - but my preference goes to the CH1 and I can't quite put my finger on why. I'm eventually going to get another CH1 in best so I can have the whole range.
Andrew you're quickly becoming a bad influence on me! Now you got me contemplating the CH1 in 2-band or 3-band!