Is a slip bag/maize ball necessary?

[Dawn-nightmarex]

Mike Tyson used a slip ball. Is it necessary? Couldn’t you just practice head movement without it while shadow boxing? Is there a difference in practicing with or without it?

[ShoulderRoll]

I don't know if it's absolutely necessary, but I will say that practicing head movement while shadowboxing isn't the same.

This thing forces you to learn REAL timing and gives you physical feedback when you don't do it right.