I would never use a device like that on any of my horses! I'd want to find out the reasons why they were bucking. Is it a physical issues, a tense unbalanced rider, insufficient schooling, horse lacking in confidence, excitement, problems with their tack...
IMHO as a rule a horse is telling you something - well actually they are shouting something to you - if they keep bucking and I think to use some kind of gadget to stop them expressing this when they could be in severe pain is completely and utterly wrong.
I can't think of a single reason for an instrument of torture like that to be used.
