[macgro7]

I think it goes on tight to their neck, it says it has very rough edges so I'm guessing causes pain if the bird try's to crow.

No no
It says it DOES NOT have rough edges. Very smooth in fact.
It's just a piece of velcro which goes around cocks neck. It doesn't affect his breathing or eating. But when he tries to crow he stretches his neck the collar stops him from stretching fully therefore the voice is not as loud as it normally would be.