no more like this with a roller at the middle
http://www.domvet.com/pharmvet/images/137.jpg
Oh - I assumed it was a snaffle type. That is a curb bit, and with the length of the shaft there, a fairly strong one, with a chin-strap on it that comes into play with any contact.
Did you switch to this bit on someone's advice who has watched him go? Was he strong in your hands with the straight snaffle?
should say ~if it has~ a chin-strap on it that comes into play with any contact.