I have used them for about a year on my boy who is very tricky and fussy on the flat. I would say they do work very well especially if you have a horse who has trouble maintaining a steady contact. In our case at least the elasticity seems to encourage him to accept the bit and take the contact forward and down.
I would say they are worth a try and if you keep an eye out on a certain well known auction site you can usually pick some up more reasonably than brand new as they are quite pricey.
Hi i used these on my mare but was advised to take them off as she was using them as a toy and not listening to my hands, there going on a certain auction site tonight