i might be wrong, but are they not the same as grass reins? as in they stop the pony putting its head down and eating, or generally just putting its head down?
might be something totally different tho so apologises if im barking up the wrong tree!!
They stop the horse form putting it's head down (i.e. when you have a kid riding if the pony decides to put his head down to eat kiddy can't really do much and may fall off but with a daisy rein the horse can't do that.)
I bought these many years ago when my daughter was a little pip-squeak. Our pony could avoid them and by contorting her head in a weird fashion could still manage to get down to the grass. They didn't rate highly with me so I took them off and donated them to someone else.
I used them on Oscar when at shows on Grass cos he used to put his head down all the time to eat, but they didint really help, you cant have them too short, cos we were jumping and he needed to strech but you cant have them long cos they wont work, and he found a way to put his head down even with them on, we took them off and have never used them since!
I have used them on a childs pony to stop it putting in the occasional buck and eating grass - they didn't help with either - he could just arch his neck in a weird way far enough to get them over to one side and then he was off!
Thats the theory but my pony got it off to a fine art,he didnt move very fast, but my god he stopped quick! They did work sometimes, probably reduced my falling off ratio a little!
I knew a riding school pony who had a daisy rein to stop him putting his head down but he used to do it anyway even with the daisy rein ... and with such violence and so suddenly that it would cause the back of the saddle to flip up. So the kids would not only be yanked forward but also catapulted out of the saddle!!!