Julia's double-jointed mouthpiece creates space for the tongue and therefore relieves it from constant pressure.
The Roller reaches further down than the joints. This increases the point-pressure on the tongue if your horse pulls or being heavy in your hand, not consistently.
It also gives the horse something to play with, which is great for horses that can feel numb to the contact. Together with the taste of sweet iron and copper, this bit is accepted even by very picky and sensitive horses. It increases acceptance and steady contact.
This bit is in good condition with the usual oxidisation that you would expect from a used sweet iron bit.