I bought 2.1" for my practice arrows. I will see how they work before I change the hunting arrows. Surprisingly, there did not seem to be much selection in vanes. I found 2.1 and 4". Currently, I am using 3".
For my recurve, I think the arrows I bought are 4" feathers. I'll have to check. I intend to buy a helical clamp for the recurve.